Sumwise

What is the Percentage Difference from 20 to 18?

From 20 to 18 is a 10% decrease

Change
-10%
Difference
-2
New ÷ old
0.9
Direction
decrease

Sumwise · Checked by Theo Abbott · Data: exact arithmetic; unit definitions from NIST SP 811 · Updated · How we check it

How to work it out

  1. Difference: 18 − 20 = -2
  2. Divide by the starting value: -2 ÷ 20 = -0.1
  3. Multiply by 100: -10%
  4. Check: Work forwards from the start: 20 × (1 − 0.1) = 20 × 0.9 = 18.

In a spreadsheet: =(18-20)/20*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 90% of the old one: for every 100 at the start there are now 90, so 10 out of every 100 have gone.

Sales: a price cut from $20 to $18 is a 10% discount.

Why the change back is different

A 10% fall followed by a 10% rise does not bring you back to 20: it gives 19.8. The second percentage is taken of 18, not of 20, so to undo this change you need 11.1111% instead.

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The other way round: Percentage difference from 18 to 20

Practice

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Calculate another

How answers are calculated and checked: methodology.

Questions

What is the Percentage Difference from 20 to 18?

Going from 20 to 18 is a 10% decrease. Formula and steps.

Is going from 20 to 18 an increase or a decrease?

A decrease: the value fell by 2, which is 10% of the starting value.

What is the percentage change from 18 back to 20?

11.1111%. It is a different number because the starting value is now 18, not 20.