Sumwise

Percentage Change from 40 to 20

From 40 to 20 is a 50% decrease

Change
-50%
Difference
-20
New ÷ old
0.5
Direction
decrease

Sumwise · Maintained by Theo Abbott (pen name) · automated checks · Data: exact arithmetic; unit definitions from NIST SP 811 · Updated · How the checks work

How to work it out

  1. Difference: 20 − 40 = -20
  2. Divide by the starting value: -20 ÷ 40 = -0.5
  3. Multiply by 100: -50%
  4. Check: Work forwards from the start: 40 × (1 − 0.5) = 40 × 0.5 = 20.

In a spreadsheet: =(20-40)/40*100. Always divide by the starting value, not the new one. A rise from 40 to 50 is +25%, but the fall from 50 back to 40 is −20%.

What the result means

The new value is 50% of the old one: for every 100 at the start there are now 50, so 50 out of every 100 have gone.

Sales: a price cut from $40 to $20 is a 50% discount.

Why the change back is different

A 50% fall followed by a 50% rise does not bring you back to 40: it gives 30. The second percentage is taken of 20, not of 40, so to undo this change you need 100% instead.

Related results

Results for nearby numbers
40 to 18

From 40 to 18 is a 55% decrease

40 to 19

From 40 to 19 is a 52.5% decrease

40 to 21

From 40 to 21 is a 47.5% decrease

40 to 22

From 40 to 22 is a 45% decrease

40 to 30

From 40 to 30 is a 25% decrease

The other way round: Percentage change from 20 to 40. Percentage change is not symmetric: from 40 to 20 is -50%, but from 20 back to 40 is 100%, because the starting value is the base. For a comparison that is the same both ways, use the percentage difference between 20 and 40: 66.6667%. See Percentage difference between 20 and 40.

Practice

8 to 59
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From 8 to 59 is a 637.5% increase

41 to 79
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From 41 to 79 is a 92.6829% increase

37 to 87
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From 37 to 87 is a 135.1351% increase

86 to 62
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From 86 to 62 is a 27.907% decrease

27 to 60
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From 27 to 60 is a 122.2222% increase

85 to 8
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From 85 to 8 is a 90.5882% decrease

Calculate another

How answers are calculated and checked: methodology.

Questions

Percentage Change from 40 to 20

Going from 40 to 20 is a 50% decrease. Formula and steps.

Is going from 40 to 20 an increase or a decrease?

A decrease: the value fell by 20, which is 50% of the starting value.

What is the percentage change from 20 back to 40?

100%. It is a different number because the starting value is now 20, not 40.