Personal finance management: precise or approximately?
If you are off by coins, how can you be sure that you only made a typo and didn't miss a transaction?  To start off, I would strongly you find a way to be precise.  It doesn't matter so much in the accounting, but the habit of doing a thorough job will pay off in other dividends down the line. Basically, do the pennies now.  Tryout some free online software to save the headache of data entry. But........ Since my primary goal is to get you to do the budgeting, and if you really hate the coins, just be consistent in how you fudge the debits and the credits. Always round down to the nearest whole in income, and always round up on expenses.  You won't overspend this way, and your back account should have a little bit of padding because you will assume less money in and more money out. Honestly, I do tracking in both Quicken and Mint.com, so the transaction size is no big deal to me.  If I did it all in Excel, I would round to whole notes.  You didn't tag your question with a country, so I don't know if or similar is available to you. "Here is what we do.  We use YNAB to do our budgeting and track our expenses.  Anything that gets paid electronically is tracked to the penny.  It really needs to be, because you want your transaction records to match your bank's transaction records. However, for cash spending, we only count the paper money, not the coins.  Here is how it works: If I want a Coke out of a vending machine for 75 cents, and I put a dollar bill in and get a quarter back as change, I record that as a $1.00 expense. If, instead, I put 3 quarters in to get the Coke, I don't record that expense at all.  Spending coins is ""free money.""  We do this mainly because it is just easier to keep track of.  I can quickly count the cash in my wallet and verify that it matches the amount that YNAB thinks I have in my wallet, and I don't need to worry about the coins.  Coins that are in my car to pay for parking meters or coins in the dish on my dresser don't need to be counted. This works for us mainly because we don't do a whole lot of cash spending, so the amount we are off just doesn't add up to a significant portion of our spending.  And, again, bank balances are exact to the penny."
"There is a saying in business: what gets measured gets done. Track every expense you make. Later, look over what you have learned. If 5% of your total budget is going to something frivolous, maybe you could halve it? If 1% or 0.1% is going to that frivolous expense, there's not much to be gained even by eliminating it. If you spend $200/mo on coffees, dropping those will help. If you spend $10/mo on coffees, you need to look elsewhere for your big savings. Have a target: I want to put $X into savings each month. Therefore I can only spend $Y. What do you have to change about last month's spending patterns to get down to $Y? Where are the easy targets for you? They will be different than the easy targets for me. What absolutely cannot change for you? Once you know the costs of what you're doing, you will know where it's possible to save, and where it's ""worth it"" to economize." Wow I honestly hope this is your first ever finance class. Anyway this isn't even finance, the only thing here finance related are the terms. It's really an algebra problem. Which is 1,312,500/x = 2 soooo find X.  X = 656250  so 131,250 in notes payable. If you don't know what to do know to find the quick ratio, then change majors As has been said before, going from nothing to something is an infinite percent increase! It is not 100%. Maybe you had a dollar and now have $101 that is a 10000% increase! Quite remarkable. I often work with symmetrized percent changes like: spc = 100 * (y2-y1)/(0.5 * (y1+y2)) Where I compute the percent with respect to the average. First this is more stable as often measurements can have noise, the average is more reliable.  Second advantage is also that this is symmetric. So going from 95 to 105 is a 10 % increase while going from 105 to 95 a 10% decrease. Of course you need to explain what you show. Your calculations are correct. It is likely that the bank's software has a rounding error.  In effect, either your bank is overstating your interest by eight cents per month, or your bank is insisting that you prepay your principal by eight cents per month.  If the bank's ongoing interest calculations are correct, your final payment will be slightly smaller (because of the prepaid principal, and because of compound interest on those prepayments).  I have performed similar calculations for my mortgages over the years, and except upon early payoff in the middle of the month, I have always matched my banks' calculations to the penny.  Ironically, this means that my banks' formulas are a bit weird: After making these adjustments, even my calculations for the mid-month payoff matched to the penny. "There are some assumptions which can be made in terms of the flexibility you have - I will start with the least flexible assumption and then move to more flexible assumptions. If you must put down a number 1, your go-to for this(""Change the start period to 1""), is pretty good, and it's used frequently for other divide-by-zero calculations like kda in a video game. The problem I have with '1' is that it doesn't allow you to handle various scales.  Some problems are dealt with in thousands, some in fractions, and some in hundreds of millions. Therefore, you should change the start period to the smallest significantly measurable number you could reasonably have. Here, that would take your example 0 and 896 and give you an increase of 89,500%. It's not a great result, but it's the best you can hope for if you have to put down a number,  and it allows you to keep some of the ""meaning in the change."" If you absolutely must put something This is the assumption that most answers have taken - you can put down a symbol, a number with a notation, empty space, etc, but there is going to be a label somewhere called 'Growth' that will exist. I generally agree with what I've seen, particularly the answers from Benjamin Cuninghma and Nath. For the sake of preservation - those answers can be summarized as putting 'N/A' or '-', possibly with a footnote and asterisk. If you can avoid the measurement entirely The root of your question is ""What do my manager and investors expect to see?"" I think it's valuable to dig even further to ""What do my manager and investors really want to know?"". They want to know the state of their investment. Growth is often a good measurement of that state, but in cases where you are starting from zero or negative, it just doesn't tell you the right information. In these situations, you should avoid % growth, and instead talk in absolute terms which mention the time frame or starting state. For example:" What are your goals? Managing your finances is not the same for everyone. For example, do you want a more hands-off approach to finance or more hands-on? Are you looking at investments as well or just saving money? Those types of questions. "Yes if and only if you properly use P/Y and C/Y.   For your familiarity, I recommend also trying it with I = 7.56% / 12, and P/Y and C/Y = 1.  I like to think of P/Y and C/Y as ""per period"" and prefer to divide the interest rate by the number of periods per year, but so long as you keep everything coherent in the solver, you will get the correct answer with both approaches." I would question whether your stated goal (of strictly controlling your expenses) is really the problem you should be tackling.  In my opinion, unless you're under financial hardship where you can barely make ends meet, you're much better off using a budget as a high-level, descriptive tool rather than a low-level, prescriptive tool. This is what I would do in your situation: After the first few months, you can start to think about high-level changes that you can make to your spending habits to get the most bang for your buck.  I wouldn't worry about the little expenses, unless they're really adding up to a sizable chunk of your total expenses.  Instead, I would look at things like: eating out too often, buying too many movies, too many impulse buys over $100, etc. Identifying patterns like that will help you make lifestyle changes that will allow you to spend less money without having to micromanage every single expense.  I have tried the micromanaged approach in the past, and it simply doesn't work for me.  There's too much overhead, and eventually I start to feel that it's just not worth it.  Think about it - is it really worth the extra time and energy required to worry about where every dollar goes all month long just to save an additional hundred bucks over what you can do with this passive approach?   I think that by focusing on the big picture, you can get within a couple percentage points of the same amount of savings as if you had micro-managed your expenses, but with much less work and mental strain. Let's put some numbers on this and see what the hourly returns are with each approach, always being optimistic about the micromanaged approach and conservative on the passive approach.   Let's assume you earn $50,000/year.  Let's also assume that if you micromanage all of your expenses, you could manage to save $5000/year beyond what you do now.  And let's say that with the passive approach, you can get within 20 percentage points instead of the 2 I stated earlier, for a savings of $4000/year.  Now what will your hourly returns look like?  The following are based on how I would personally use both systems, so your numbers may vary a bit. Micromanaged Budgeting Savings = $5000 per year = $416.67 per month  Time spent = 15-30 minutes per day = 7.5 - 15 hours per month  Hourly return = $27.78 - $55.56  Passive Budgeting Savings = $4000 per year = $333.33 per month  Time spent = 1 - 2 hours per month Hourly return = $166.67 - $333.33 So clearly the passive approach gives a substantially higher hourly return, even though it gives a lower absolute return.  Maybe more importantly though, if passive budgeting opens up an extra 10 hours a month, you could potentially put those hours into your job and make an extra (10 hours * $25/hour) = $250 a month, or $3000 per year, assuming no extra pay for overtime.  So that means that the passive budgeting approach would actually allow you to save ($4000 + $3000 * .75) = $6250 per year, compared to the $5000 you would save by micromanaging. If you're in a situation where you can't put those hours into more work and you really need that extra $83.34 per month to help make ends meet, then by all means micromanage your expenses and try to save as much as possible.  But if either of the previous conditions are not true for you, you're much better off, in my opinion, using a passive budget. "I argued for a 15% rule of thumb here: Saving for retirement: How much is enough? Though if you'll let me, I'd refine the argument to: use a rule of thumb to set your minimum savings, then use Monte Carlo to stress-test and look at any special circumstances, and make a case to save more. You're right that the rule of thumb bakes in tons of assumptions (great list btw). A typical 15%-works scenario could include: If any of those big assumptions don't apply to you (or you don't want to rely on them) you'd have to re-evaluate. It sounds like you're assuming 4-5% investment returns? As you say that's probably the big difference, 4-5% is lower than most would assume. 6-7% (real return) is maybe a middle-of-the-road assumption and 8% is maybe an unrealistic one. Many of the assumptions you list (such as married/kids, cost of living, spouse's income, paying for college) can maybe be bundled up into one assumption (percentage of income you will spend). Set a percentage budget and as you go along, stay within your means by sacrificing as required. Also smooth out income across layoffs and things by having an emergency fund. By staying on-budget as you go you can remove some of the unpredictability. The reason I think the rule of thumb is still good, despite the assumptions, is that I don't think a ""more accurate"" number based on a lot of unpredictable guesses is really better; and it may even be harmful if you use it to justify saving less, or even if you use it to save far too much. See also http://en.wikipedia.org/wiki/Precision_bias Many (most?) important assumptions are not predictable: investment returns, health care inflation, personal health, lifestyle creep (changing spending needs/desires), irrational investment behavior. I agree with you that for many scenarios and people, 15% will not be enough, though it's a whole lot more than most save already. In particular, low investment returns over your time horizon will make 15% insufficient, and some argue that low investment returns over the coming 30 years are likely. Without a doubt, 20% or more is safer than 15%. Do consider that ""saving enough"" is not a binary thing. If you save only 15% and it turns out that doesn't completely replace your income, it's not like you're out on the street; you might have to retire a few years later, or downsize your house, or something, but perhaps that isn't a catastrophe. There's a very personal question about how much to sacrifice now for less risk of sacrifice in the future. Maybe I'd better qualify ""not a binary thing"": some savings rates (certainly, anything less than 10%), make major sacrifices pretty likely... so in that sense there is a binary distinction between ""plausible plan"" and ""denial."" Also, precise assumptions and calculations get a lot more useful as you approach retirement age. You can pretty much answer the question ""is it reasonable to retire right now?"" or ""could I retire in 5 years?"" (though with a retirement that could last 30 years, plenty of unknowns will remain even then). I think at age 20 or 30 though, just saving 15% (20% if you're conservative), and not spending too much time on a speculative analysis would be a sound decision. That's why I like the rule of thumb. Analysis paralysis (saving nothing or near-nothing) is the real danger early in one's career. Any plausible percentage is fine as long as you save. As your life unfolds and you see what happens, you can refine and correct, adjusting your savings rate, moving your retirement age around, spending a little less or more. The important thing earlier in life is to just get in the right ballpark." There is a way to get a reasonable estimate of what you still owe, and then the way to get the exact value. When the loan started they should have given you amortization table that laid out each payment including the principal, interest and balance for each payment. If there are any other fees included in the payment those also should have been detailed. Determine how may payments you have maid: did you make the first payment on day one, or the start of the next month? Was the last payment the 24th, or the next one? The table will then tell you what you owe after your most recent payment. To get the exact value call the lender. The amount grows  between payment due to the interest that is accumulating. They will need to know when the payment will arrive so they can give you the correct value. To calculate how much you will save do the following calculation: payment = monthly payment for principal and interest paymentsmade =Number of payments made = 24 paymentsremaining = Number of payments remaining = 60 - paymentsmade = 60-24 = 36 instantpayoff = number from loan company  savings = (payment * paymentsremaining ) - instantpayoff "If the wording is ""within 10 days"" then its 10 days. Calendar days. Otherwise they would put ""10 business days"", for example. Usually, if you need to do something within 10 days from today, the first day to count is today. I would expect ""within"" to mean that you can fund in any of the days up to the 10th. But that's me, trying to read English as English. Why don't you call the bank and ask them?" If you want to keep any consistent standard, you need to knuckle down and make those transaction entries. Honestly, this is a lot faster doing in bulk than doing day-by-day.  But change how you account so it isn't annoying.  I minimize my bookable transactions.  For instance I deposit all income whole (for tracking) but stop tracking when the money is converted to cash or gift card money - I log adding $50 to a McDonalds gift card, but not the individual meals.  I only use cash for the myriad small things I do not want to track - fast food, parking meters, etc.  Anything big or that I want to track goes on a credit card.  Then it's easy to reconcile credit cards to accounting system.   (Cathy) Ryan's Law: if it wasn't written down, it didn't happen. Here's a link with comparison of various online and offline PF software: http://personalfinancesoftwarereviews.com/compare-personal-finance-software/ "VaR is statistical, so you can set the confidence interval to 5%, 1%, 0.01%, etc. VaR is the same thing as standard deviation applied over a specific time frame, its just a matter how you come up with it. For example the 95% VaR is something like 1.65 standard deviations of the returns. as you increase the number of std dev (Z score), you're confidence interval widens and you capture more of the outliers. if you set it to 99.99%, you can envision the return distributions for all but the .01%. choose between the 2? VaR is more practical on a day to day, but shortfall is better for extreme events, like 2008 when lehman collapsed or the russian debt crisis when yields blew out.  VaR has a lot of caveats about it, in that it considers everything ""under normal market conditions"". reality is, under normal market conditions, you're less concerned about risk. you want to know expectations when things go really wrong. VaR is best used as part of a risk management package, in conjunction with stress tests, duration/ DV01, liquidity analysis, etc, but its sort of leaves a lot of holes as a standalone. from a reporting and regulatory standpoint, VaR is generally accepted, and many firms reporting one day VaR in their financials (JPM, Goldman).  tracking error tends to be company specific. from what i've seen, its mostly funds who have to manage to a benchmark, like a pension or FoF with a specific mandate, so they can't have too much deviation from that. you'll see this with beta too, but its the same idea.   capital adequacy is slightly different from market risk. your PB or whoever will asses your portfolio holdings and apply a haircut to them based on risk and liquidity. for example you'll get close to 100% margin credit for stocks, but only a fraction of that applied to your account for a CDO^2 since liquidity is non-existent." "The other answers are good, I would just like to add certain points, taking this question together with the previous ones you have asked here. How can a person measure how much to spend on food, car, bills or rent   from his salary? Is there a formula to keep in check? Basically, it may well be that your best option would be to move to a smaller apartment or worse location to bring down rent, possibly forget about your own study in the worst case, sell the car and use public transportation, eat as many meals as possible at home, bring boxed lunch from home to work, if this applies, etc -- whatever makes a saving and sense to you. Regarding food, this is the point where it is usually possible to save a very significant amount, if you are prepared to make food at home. Unless you are already doing it, look around for articles such as ""living on 20 pounds a week"" or so, maybe they will give you ideas you can use (eg. How to eat on 10 pounds a week: shopping list and recipes) -- where you are shopping is crucial here as similar items can differ in price significantly between different chains. If the electricity bill is significant and you are at home a lot, you could try to bring it down by changing all bulbs in your home to LED ones, unless it has already been done. Yes, they can cost 2-3 more than eg. halogen ones, but they use 5-10x less electricity. Forget credit cards, if possible. Use debit cards so you know the money you spend does not get you into more debt. One question you asked here was about exchange rates -- if you work with different currencies a lot, there are several companies such as Revolut or N26, which offer accounts with debit cards that use near FX rates --- in my experiencee I could save around 10-15% on currency conversion EUR/GBP, using Revolut, compared to my local bank rate, for example. I find myself looking at my account every single day and get tensed   and sad because almost whenever the money (pay) comes in I freak out   that after everything there is nothing for us to enjoy or save. Well, yes. That is nearly the definition of too much debt. The point about going to the extremes of reducing expenses I outlined above, is that the more you can reduce your expenses while struggling with debt, the faster you'll get out of it. It might be hard to adapt, but it will be better, if you can calculate how long it will take to get you back on feet and know that, eg. ""in 6 months I can start to think of savings and carefully upgrading my lifestyle back"".  In turn, the smaller the reduction of expenses, the more prolonged the process -- you might be looking at 2-3 years of insecure/constantly frustrating/risking more debt lifestyle, instead of 6 months of severely reduced one. Alternatively, if things go too bleak, you might consider declaring bankrupcy -- although I am not sure how feasible it is in the UK."