Iffwil has an area of 5.06 km² (1.95 sq mi).
Of this area, 2.79 km² (1.08 sq mi) or 55.1% is used for agricultural purposes, while 1.84 km² (0.71 sq mi) or 36.4% is forested.
 Of the rest of the land, 0.4 km² (0.15 sq mi) or 7.9% is settled (buildings or roads).

Of the built up area, housing and buildings made up 2.6% and transportation infrastructure made up 5.1%.
Out of the forested land, all of the forested land area is covered with heavy forests.
Of the agricultural land, 46.8% is used for growing crops and 6.7% is pastures, while 1.6% is used for orchards or vine crops.

The municipality is located on the Rapperswil plateau.

On 31 December 2009 Amtsbezirk Fraubrunnen, the municipality's former district, was dissolved.
On the following day, 1 January 2010, it joined the newly created Verwaltungskreis Bern-Mittelland.
Iffwil has an area of 5.06 km² (1.95 sq mi). Of this area, 2.79 km² (1.08 sq mi) or 55.1% is used for agricultural purposes, while 1.84 km² (0.71 sq mi) or 36.4% is forested.  Of the rest of the land, 0.4 km² (0.15 sq mi) or 7.9% is settled (buildings or roads).
Of the built up area, housing and buildings made up 2.6% and transportation infrastructure made up 5.1%. Out of the forested land, all of the forested land area is covered with heavy forests. Of the agricultural land, 46.8% is used for growing crops and 6.7% is pastures, while 1.6% is used for orchards or vine crops.
The municipality is located on the Rapperswil plateau.
On 31 December 2009 Amtsbezirk Fraubrunnen, the municipality's former district, was dissolved. On the following day, 1 January 2010, it joined the newly created Verwaltungskreis Bern-Mittelland.
Iffwil