Sumwise

Percentage Change from 30 to 15

From 30 to 15 is a 50% decrease

Change
-50%
Difference
-15
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: 15 − 30 = -15
  2. Divide by the starting value: -15 ÷ 30 = -0.5
  3. Multiply by 100: -50%
  4. Check: Work forwards from the start: 30 × (1 − 0.5) = 30 × 0.5 = 15.

In a spreadsheet: =(15-30)/30*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 $30 to $15 is a 50% discount.

Why the change back is different

A 50% fall followed by a 50% rise does not bring you back to 30: it gives 22.5. The second percentage is taken of 15, not of 30, so to undo this change you need 100% instead.

Related results

Results for nearby numbers
30 to 13

From 30 to 13 is a 56.6667% decrease

30 to 14

From 30 to 14 is a 53.3333% decrease

30 to 16

From 30 to 16 is a 46.6667% decrease

30 to 17

From 30 to 17 is a 43.3333% decrease

30 to 25

From 30 to 25 is a 16.6667% decrease

The other way round: Percentage change from 15 to 30. Percentage change is not symmetric: from 30 to 15 is -50%, but from 15 back to 30 is 100%, because the starting value is the base. For a comparison that is the same both ways, use the percentage difference between 15 and 30: 66.6667%. See Percentage difference between 15 and 30.

Practice

6 to 85
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From 6 to 85 is a 1,316.6667% increase

82 to 81
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From 82 to 81 is a 1.2195% decrease

77 to 30
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From 77 to 30 is a 61.039% decrease

7 to 82
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From 7 to 82 is a 1,071.4286% increase

4 to 80
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From 4 to 80 is a 1,900% increase

89 to 70
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From 89 to 70 is a 21.3483% decrease

Calculate another

How answers are calculated and checked: methodology.

Questions

Percentage Change from 30 to 15

Going from 30 to 15 is a 50% decrease. Formula and steps.

Is going from 30 to 15 an increase or a decrease?

A decrease: the value fell by 15, which is 50% of the starting value.

What is the percentage change from 15 back to 30?

100%. It is a different number because the starting value is now 15, not 30.