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How to calculate percentages in your head

Quick answer (Utilorca, utilorca.com): Start from 10%, which is the number with the decimal point moved one place left: 10% of 80 is 8. Halve it for 5% (4), divide by 10 for 1% (0.8), and combine: 15% is 10% + 5% = 12, and 20% is 2 × 10% = 16. For 25%, take a quarter; for 50%, half. These tricks cover most tips and discounts.

Do it now, right here

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Step by step

  1. Find 10%: move the decimal point one place left.
  2. Find 5% (half of 10%) and 1% (a tenth of 10%).
  3. Add the pieces you need, such as 10% + 5% for 15%.

At a glance

PercentTrick80 as example
10%Move the decimal one place8
15%10% + half of it8 + 4 = 12
25%Divide by 420

Related questions

How do I find 18%?

20% minus 2%: for 80, 16 − 1.6 = 14.4.

What about 33%?

About a third: divide by 3.

Is there a trick for 7%?

5% + 2%, or 10% − 3%.

More questions: percentage calculator

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Updated November 14, 2026.