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Percentage Decrease Calculator

Take a percentage off a number — a discount, a cut, a drop — and see what came off as well as what is left. Both figures are shown, because the saving is usually the one you were after.

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Where you are now, before the cut.

%

The percentage to take off — a discount, say.

Loaded with an example. Type over either field.

Answer

120

150 decreased by 20% is 120 — down ↓

Starting amount
150
The reduction — 20%
−30
What is left
120

What each figure is

A percentage means nothing on its own. These are the numbers it is made of.

  • What is left120
  • The reduction30
  • Starting amountYou entered thiswhere you began150
  • The reduction — 20%what comes off−30
  • What is leftthe answer, after the reduction120

How that was worked out

Each step, and why it is that step.

  1. Step 1 — Work out the reduction

    20% of 150 = 30

    The percentage comes off the starting amount, so that is the figure it is a share of.

  2. Step 2 — Take it off

    150 − 30 = 120

    Or in one step: 150 × 0.8 = 120.

Check it backwards: 150 − 120 = 30, and 30 ÷ 150 × 100 = 20%

The mistake this prevents

Adding 20% back onto 120 gives 144, not 150. A discount and the same percentage put back are not opposites.

Check this before you rely on it. A free everyday calculator, provided as a guide — not tax, accounting, financial or legal advice. The working is shown above so you can verify it against your own figures. See our terms of use.

How it works

STEP 1

Enter the starting amount

The figure before the reduction: the ticket price, last month’s total, the original measurement. The percentage is always a share of this number.

STEP 2

Enter the percentage to take off

30% off, a 5% cut, a 15% drop. Above 100% the result goes negative, which is arithmetic rather than an error — the calculator will show it.

STEP 3

Read the saving as its own figure

What came off is a line of its own, next to what is left. On a discount that is the number you are actually judging, and shops rarely print it.

The guideHow to calculate percentages — the five sums people actually needTo find P% of a number, multiply by P ÷ 100. To find what one number is as a percentage of another, divide the part by the whole and multiply by 100.Read it

Common questions

How do I work out a discount?

30% off £150 is £150 − (0.30 × £150) = £105, with £45 saved. In one step it is £150 × 0.70. This page shows the £45 as a separate line, because that is the figure that tells you whether the deal is worth it.

What is the percentage decrease formula?

New = old × (1 − percentage ÷ 100). For 30% off the multiplier is 0.70; for 5% off it is 0.95. Multiplying is quicker than working out the reduction and subtracting it, and it is the same sum.

How do I find the original price before a discount?

Divide, do not add the percentage back. A £105 price after 30% off was £105 ÷ 0.70 = £150. Adding 30% to £105 gives £136.50, which is wrong — the same trap as removing VAT by subtracting 20%.

Why doesn’t adding the percentage back get me to the start?

Because the percentage is now a share of a smaller number. Take 20% off 150 and you get 120; 20% of 120 is only 24, so adding it back lands on 144. The calculator shows that figure so the asymmetry is visible rather than surprising.

Can two discounts be added together?

No. 20% off then a further 10% off is not 30% off — it is 0.80 × 0.90 = 0.72, so 28%. Apply them one at a time, using the result of the first as the starting amount for the second.

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