user90567: From https://bitcoinfees.earn.com/ I can see a list of bitcoin satoshi fees/byte
From https://thenextweb.com/hardfork/2018/07/12/bitcoin-block-size/ I can see that we can have block sizes of up to 2mb with segwit.
If I assume that segwit adoption increases in the next year, then I will base all calculations on the block size being ~2mb. 
How do I back-of-envelope calculate total fees in bitcoin spent daily? 
Assuming 6 blocks / hour, & with 24 hours in a day, is it:
~satoshiFee * 2m * 6 * 24
Which, assuming an average satoshi fee of 10 (using https://bitcoinfees.info/)
Gives:
10 * 2m * 6 * 24
And in BTC that's divided by 10^8, so we'd get:
20m * 144 / 10^8 = 28.8
Is that correct?

user60443: Yes that look correct.
From https://bitcoinfees.info/, the current average fee rate listed at the bottom of the chart is 24 satoshis/byte. To calculate the total fees in a day you want fee rate * total bytes = total satoshis.
Assuming 2MB block size,
fee rate = 24 satoshis/byte
total bytes = 2MB * 6 * 24 = 288MB
total btc = total satoshis / 1e8
total btc = (24 * 288M) / 1e8 = 69.12 BTC

90567: <p>From <a href="https://bitcoinfees.earn.com/" rel="nofollow noreferrer">https://bitcoinfees.earn.com/</a> I can see a list of bitcoin satoshi fees/byte</p>

<p>From <a href="https://thenextweb.com/hardfork/2018/07/12/bitcoin-block-size/" rel="nofollow noreferrer">https://thenextweb.com/hardfork/2018/07/12/bitcoin-block-size/</a> I can see that we can have block sizes of up to 2mb with segwit.</p>

<p>If I assume that segwit adoption increases in the next year, then I will base all calculations on the block size being ~2mb. </p>

<p>How do I back-of-envelope calculate total fees in bitcoin spent daily? </p>

<p>Assuming 6 blocks / hour, &amp; with 24 hours in a day, is it:</p>

<p>~satoshiFee * 2m * 6 * 24</p>

<p>Which, assuming an average satoshi fee of 10 (using <a href="https://bitcoinfees.info/" rel="nofollow noreferrer">https://bitcoinfees.info/</a>)</p>

<p>Gives:</p>

<p>10 * 2m * 6 * 24</p>

<p>And in BTC that's divided by 10^8, so we'd get:</p>

<p>20m * 144 / 10^8 = 28.8</p>

<p>Is that correct?</p>
 60443: <p>Yes that look correct.</p>

<p>From <a href="https://bitcoinfees.info/" rel="nofollow noreferrer">https://bitcoinfees.info/</a>, the current average fee rate listed at the bottom of the chart is 24 satoshis/byte. To calculate the total fees in a day you want <code>fee rate</code> * <code>total bytes</code> = <code>total satoshis</code>.</p>

<p>Assuming 2MB block size,</p>

<p><code>fee rate</code> = <code>24 satoshis/byte</code><br>
<code>total bytes</code> = <code>2MB * 6 * 24</code> = <code>288MB</code></p>

<p><code>total btc</code> = <code>total satoshis / 1e8</code><br>
<code>total btc</code> = <code>(24 * 288M) / 1e8</code> = <code>69.12 BTC</code></p>
