Sumwise

Percentage Change from 80 to 40

From 80 to 40 is a 50% decrease

Change
-50%
Difference
-40
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: 40 − 80 = -40
  2. Divide by the starting value: -40 ÷ 80 = -0.5
  3. Multiply by 100: -50%
  4. Check: Work forwards from the start: 80 × (1 − 0.5) = 80 × 0.5 = 40.

In a spreadsheet: =(40-80)/80*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 $80 to $40 is a 50% discount.

Why the change back is different

A 50% fall followed by a 50% rise does not bring you back to 80: it gives 60. The second percentage is taken of 40, not of 80, so to undo this change you need 100% instead.

Related results

Results for nearby numbers
80 to 38

From 80 to 38 is a 52.5% decrease

80 to 39

From 80 to 39 is a 51.25% decrease

80 to 41

From 80 to 41 is a 48.75% decrease

80 to 42

From 80 to 42 is a 47.5% decrease

80 to 50

From 80 to 50 is a 37.5% decrease

The other way round: Percentage change from 40 to 80. Percentage change is not symmetric: from 80 to 40 is -50%, but from 40 back to 80 is 100%, because the starting value is the base. For a comparison that is the same both ways, use the percentage difference between 40 and 80: 66.6667%. See Percentage difference between 40 and 80.

Practice

15 to 19
Show answer

From 15 to 19 is a 26.6667% increase

27 to 30
Show answer

From 27 to 30 is a 11.1111% increase

72 to 82
Show answer

From 72 to 82 is a 13.8889% increase

99 to 5
Show answer

From 99 to 5 is a 94.9495% decrease

2 to 84
Show answer

From 2 to 84 is a 4,100% increase

64 to 74
Show answer

From 64 to 74 is a 15.625% increase

Calculate another

How answers are calculated and checked: methodology.

Questions

Percentage Change from 80 to 40

Going from 80 to 40 is a 50% decrease. Formula and steps.

Is going from 80 to 40 an increase or a decrease?

A decrease: the value fell by 40, which is 50% of the starting value.

What is the percentage change from 40 back to 80?

100%. It is a different number because the starting value is now 40, not 80.