Free · Percentages calculators 💯

Percentage of a Percentage & Amount

Combine two successive percentage proportions and calculate the amount remaining after each proportion.

  • Formula & worked example
  • Private in your browser
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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

Private by default

Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.

Formula and method

40% of 25% is 10%. Applied to an original amount of 800, the first 25% gives 200 and 40% of that gives 80.

Combined % = first % × second % ÷ 100; final amount = original amount × first % ÷ 100 × second % ÷ 100

Worked example

Enter these known values and leave the other values blank.

First proportion
25 %
Second proportion
40 %
Original amount
800
Combined proportion
10 %
After first proportion
200
After both proportions
80

Assumptions and limitations

  • Both percentage inputs are proportions to take, not percentages to subtract. For two discounts of 25% and 40%, enter the remaining proportions 75% and 60% instead.
  • The second proportion applies to the first result. Multiplying two percentage numbers requires dividing their product by 100 to express the combined result in percent.
  • Signed percentages and values over 100% are accepted as arithmetic multipliers. Interpret them according to the quantities being modeled.
  • A zero multiplier gives zero downstream. Reversing a zero multiplier cannot determine a unique original amount.

Common questions

Do I add the two percentages?

No. Taking 40% of 25% multiplies 0.40 by 0.25, giving 0.10 or 10%.

Can I model successive discounts?

Use the percentages retained after each discount. Keeping 75% and then 60% keeps 45% overall, which corresponds to a 55% total discount.

References

The calculation equations, inverse formulas, units, and input rules were imported from this source. Bookify provides the interface and equation solver.

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