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Ratio to Percentage Calculator

Convert a ratio A:B to the percentage that A makes up of the total of A and B.

What this tool does

Convert a ratio A:B to the percentage that A makes up of the total of A and B. You fill in these fields: First part (A) and Second part (B). It shows A as a percentage of the total, B as a percentage of the total, total of A and B, and A as a percentage of B.

Inputs

  • First part (A): A number. Must be at least 0. The number before the colon.
  • Second part (B): A number. Must be at least 0. The number after the colon. A and B together cannot both be 0.

How to use

  1. Enter the first part (A).
  2. Enter the second part (B).
  3. Read the result: A as a percentage of the total, B as a percentage of the total, total of A and B, and A as a percentage of B. It appears once every required field has a valid value.

Worked examples

Example 1. Inputs:

  • First part (A): 30
  • Second part (B): 70

Results:

  • A as a percentage of the total: 30.00%
  • B as a percentage of the total: 70.00%
  • Total of A and B: 100
  • A as a percentage of B: 42.86%

How this is worked out: Percentage = A / (A + B) x 100 = 30 / (30 + 70) x 100 = 30 / 100 x 100 = 30.

Example 2. Inputs:

  • First part (A): 3
  • Second part (B): 2

Results:

  • A as a percentage of the total: 60.00%
  • B as a percentage of the total: 40.00%
  • Total of A and B: 5
  • A as a percentage of B: 150.00%

How this is worked out: Percentage = 3 / (3 + 2) x 100 = 3 / 5 x 100 = 0.6 x 100 = 60.

Example 3. Inputs:

  • First part (A): 1
  • Second part (B): 3

Results:

  • A as a percentage of the total: 25.00%
  • B as a percentage of the total: 75.00%
  • Total of A and B: 4
  • A as a percentage of B: 33.33%

How this is worked out: Percentage = 1 / (1 + 3) x 100 = 1 / 4 x 100 = 0.25 x 100 = 25. The B share is 100 - 25 = 75.

Example 4. Inputs:

  • First part (A): 2.5
  • Second part (B): 7.5

Results:

  • A as a percentage of the total: 25.00%
  • B as a percentage of the total: 75.00%
  • Total of A and B: 10
  • A as a percentage of B: 33.33%

How this is worked out: Percentage = 2.5 / (2.5 + 7.5) x 100 = 2.5 / 10 x 100 = 0.25 x 100 = 25. Decimal parts are allowed.

Where this comes from

Two parts as shares of their total. The two parts are added to make the total, and each part is taken as a percent of that total. The first part is also taken as a percent of the second, when the second is not 0.

What percent one number is of another. The part is multiplied by 100 and divided by the whole. The whole cannot be 0. Source: Arithmetic: a percent is a number of parts in one hundred, so part / whole x 100.

Limitations

  • The main result reads A:B as two parts of one total, so 1:4 gives 20%. The A as a percentage of B card gives the other reading, 25%, and needs a B that is not 0.
  • Negative numbers are not accepted.

FAQs

Q: How do I read a ratio of 3:2 as a percentage?
A: The total is 3 + 2 = 5, and 3 / 5 x 100 = 60. So the first part is 60% of the total and the second part is 40%.
Q: Can I enter decimal numbers?
A: Yes. Parts can be decimals, as long as neither is negative.
Q: What if both parts are 0?
A: The tool cannot show a percentage, because there is no total to compare against. Enter a first or second part that is not 0.

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