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What is the Percentage Difference from 100 to 99?

From 100 to 99 is a 1% decrease

Step by step

  1. Difference: 99 − 100 = -1
  2. Divide by the starting value: -1 ÷ 100 = -0.01
  3. Multiply by 100: -1%

How the answer is worked out

Percentage change measures a difference against the value you started with. The value went from 100 to 99, a difference of 1. Compared with the starting value of 100, that difference is 1%, so this is a 1% decrease.

The new value is 99% of the old one: for every 100 at the start there are now 99, so 1 out of every 100 have gone.

Why calculate this?

Percentage change compares a new value with an old one regardless of size: price rises, growth, discounts, score changes.

  • Sales: a price cut from $100 to $99 is a 1% discount.
  • Weight: going from 100 to 99 kilograms is a loss of 1% of the starting weight.
  • Results: if a team scores 99 points this season after 100 last season, its total has dropped by 1%.

A quicker way

Find 1% of the starting value: 100 ÷ 100 = 1. The difference of 1 is 1 of those steps.

Percentage change is not the same as percentage points. If a rate moves from 100% to 99%, it changes by 1 percentage points, but by 1% relative to where it started.

Check the answer

Work forwards from the start: 100 × (1 − 0.01) = 100 × 0.99 = 99. Getting 99 shows the answer is right.

Rounding

Rounded to a whole number the change is -1, to one decimal place -1.0 and to two decimal places -1.00. Round only at the end: rounding halfway through a calculation can change the last digit.

The formula explained

percentage change = (new value − old value) ÷ old value × 100. A positive result is an increase and a negative result is a decrease. The old value is always the base, which is why the change from A to B and from B to A are different percentages.

Another worked example: 19 to 63

  1. Difference: 63 − 19 = 44
  2. Divide by the starting value: 44 ÷ 19 = 2.315789
  3. Multiply by 100: 231.5789%

Why the change back is different

A 1% fall followed by a 1% rise does not bring you back to 100: it gives 99.99. The second percentage is taken of 99, not of 100, so to undo this change you need 1.0101% instead.

Other ways to ask this

The same calculation is often asked in other words. All of these have the answer above:

  • Percentage decrease from 100 to 99
  • What percent less is 99 than 100?
  • 100 to 99 as a percent change
  • How much did 100 fall going to 99, in percent?
  • Relative change between 100 and 99

Terms used on this page

  • Old value: the starting amount, used as the base of the percentage.
  • New value: the amount after the change.
  • Increase: a positive change: the new value is bigger.
  • Percentage point: the plain difference between two rates, not a relative change.

The answer in other forms

Change-1%
Difference-1
New ÷ old0.99
Directiondecrease

Related results

100 to 97

From 100 to 97 is a 3% decrease

100 to 98

From 100 to 98 is a 2% decrease

100 to 101

From 100 to 101 is a 1% increase

100 to 109

From 100 to 109 is a 9% increase

The other way round: Percentage difference from 99 to 100

Doing it in a spreadsheet

In Excel, Google Sheets or Numbers type =(99-100)/100*100 into any cell. Replace the numbers with cell references (for example A1 and B1) to reuse the formula for a whole column.

Common mistakes

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%.

Practice examples

19 to 63
Show answer

From 19 to 63 is a 231.5789% increase

87 to 21
Show answer

From 87 to 21 is a 75.8621% decrease

53 to 85
Show answer

From 53 to 85 is a 60.3774% increase

78 to 69
Show answer

From 78 to 69 is a 11.5385% decrease

18 to 27
Show answer

From 18 to 27 is a 50% increase

48 to 28
Show answer

From 48 to 28 is a 41.6667% decrease

12 to 68
Show answer

From 12 to 68 is a 466.6667% increase

93 to 16
Show answer

From 93 to 16 is a 82.7957% decrease

56 to 16
Show answer

From 56 to 16 is a 71.4286% decrease

46 to 99
Show answer

From 46 to 99 is a 115.2174% increase

Calculate another

How this answer was calculated

The result is worked out from the numbers in this page's address when the page is opened, using exact arithmetic wherever possible and rounding only for display. Nothing is copied from a printed table. If you think an answer is wrong, please tell us through the contact page and we will check it.

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Questions

What is the Percentage Difference from 100 to 99?

Going from 100 to 99 is a 1% decrease. Formula and steps.

Is going from 100 to 99 an increase or a decrease?

A decrease: the value fell by 1, which is 1% of the starting value.

What is the percentage change from 99 back to 100?

1.0101%. It is a different number because the starting value is now 99, not 100.

What is the percentage difference between 100 and 99?

When neither value is the starting point, use the average as the base: 1 ÷ 99.5 × 100 = 1.005%. That is the symmetric percentage difference.

How do I calculate percentage change in Excel or Google Sheets?

Put the old value in A1 and the new value in B1, then type =(B1-A1)/A1 and format the cell as a percentage. For these numbers it shows -1%.