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Ratio to Decimal Calculator

Convert ratios in the form A:B to their decimal equivalent.

What this tool does

Convert ratios in the form A:B to their decimal equivalent. You fill in these fields: Part A and Part B. It shows decimal.

Inputs

  • Part A: A number. Starts at 3. The number before the colon.
  • Part B: A number. Starts at 4. The number after the colon. It cannot be 0.

How to use

  1. Enter the part A.
  2. Enter the part B.
  3. Read the result: decimal. It appears once every required field has a valid value.

Worked examples

Example 1. Inputs:

  • Part A: 3
  • Part B: 4

Results:

  • Decimal: 0.75

How this is worked out: Percent = 3 / 4 x 100 = 75. Decimal = percent / 100 = 75 / 100 = 0.75 (4 x 0.75 = 3).

Example 2. Inputs:

  • Part A: 5
  • Part B: 8

Results:

  • Decimal: 0.625

How this is worked out: Percent = 5 / 8 x 100 = 500 / 8 = 62.5. Decimal = 62.5 / 100 = 0.625 (8 x 0.625 = 5).

Example 3. Inputs:

  • Part A: 1.5
  • Part B: 2.5

Results:

  • Decimal: 0.6

How this is worked out: Percent = 1.5 / 2.5 x 100 = 150 / 2.5 = 60. Decimal = 60 / 100 = 0.6, the same as 1.5 / 2.5 = 0.6 (2.5 x 0.6 = 1.5).

Example 4. Inputs:

  • Part A: 7
  • Part B: 16

Results:

  • Decimal: 0.4375

How this is worked out: Percent = 7 / 16 x 100 = 700 / 16 = 43.75 (16 x 43.75 = 700). Decimal = 43.75 / 100 = 0.4375.

Where this comes from

A ratio as a decimal. The first part of the ratio is divided by the second. The second part cannot be 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

  • Part B cannot be 0, because division by 0 is undefined.
  • A repeating decimal such as 1 : 3 (0.333...) is shown as a finite number of digits, so it is an approximation.

FAQs

Q: What does the decimal mean?
A: It is Part A divided by Part B. The ratio 3:4 gives 0.75, which means Part A is three-quarters of Part B.
Q: Can I enter decimals?
A: Yes. The division works the same way, so 1.5 : 2.5 gives 0.6, the same as 3:5.
Q: Why is no result shown when Part B is 0?
A: A ratio cannot be divided by 0. The tool shows a message instead of a decimal until Part B is a number other than 0.
Q: Can I enter negative numbers?
A: Yes. A negative Part A or a negative Part B gives a negative decimal.

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