Percentage Calculation
💡Start from 10% — it is just the number with the decimal moved one place. Build every other percentage from 10%, 5% and 1% chunks.
Try it — find a percentage
liveStart from 10%, then scale.
- 1
Find 10% (move the decimal one place)
10% of 240 = 24
- 2
Scale 10% up to 35%
24 × 3.5 = 84
⏱️ Practice against the clock
A worked example
35% of 240: 10% is 24, so 30% is 72; 5% is half of 24, which is 12. Add them for 84.
Everything hangs off 10%
Ten percent is free: shift the decimal one place and there it is. Once you can grab 10% without thinking, most other percentages are a couple of easy hops away. Five percent is half of it. One percent is one more shift.
Take 35% of 240. Ten percent is 24, so 30% is 72. Five percent is half of 24, which is 12. Add them: 84. You never touched an ugly decimal, you just stacked up pieces you could see.
Flip it when it looks awkward
X% of Y is always the same as Y% of X, since both are just X times Y over 100. That little bit of symmetry turns a nasty problem into an obvious one.
8% of 50 makes you stop and think. But 50% of 8? That is 4, no effort at all. Whenever one of the two numbers is friendly, like 50 or 25 or 10, swap the roles and let it do the work.
Questions people ask
What is the single most useful percentage to know? ▾
10%. Once you can find 10% instantly you can reach almost any other percentage by halving, doubling, or adding a 1% piece.
Does the order of the numbers matter? ▾
No. X% of Y always equals Y% of X, so if one direction looks easier, flip it. 8% of 50 is awkward, but 50% of 8 is just 4.