What is the formula for the Ratio Calculator?

Missing value X (A:B = C:X) = B × C ÷ A; A ÷ B = A ÷ B; A as a share of A + B = A ÷ (A+B) × 100. The calculator applies it to the values you enter and shows the missing value x (A:B = C:X).

How to calculate ratio calculator?

Fill in a, b and c in the Ratio Calculator above and your missing value x (A:B = C:X) is calculated instantly. Change any value to see how the result responds.

What do I need to enter in the Ratio Calculator?

A, B and C. The missing value x (A:B = C:X) updates as soon as you change a value.

Ratio Calculator

Solve A:B = C:X, find the missing value of a ratio and see it as a decimal and a percentage.Math · Ratios

Quick answer

If a is 3, b is 4 and c is 12, the missing value x (A:B = C:X) is 16, the a ÷ b is 0.75 and the a as a share of a + b is 42.86 %.

Formula: Missing value X (A:B = C:X) = B × C ÷ A; A ÷ B = A ÷ B; A as a share of A + B = A ÷ (A+B) × 100.

Enter your values

Missing value X (A:B = C:X)

Calculated directly from the values you entered above.

1.8% is a ÷ B

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See how the result changes

Each table re-runs this calculator with one value changed and everything else left as it is.

Missing value X (A:B = C:X) by a

If a goes from 3 to 4.5, missing value x (A:B = C:X) changes from 16 to 10.6667 (−33%).

Missing value X (A:B = C:X) for different values of A
A	Missing value X (A:B = C:X)
1.5	32
2.25	21.3333
3start	16
4.5	10.6667
6	8

Missing value X (A:B = C:X) by b

If b goes from 4 to 6, missing value x (A:B = C:X) changes from 16 to 24 (+50%).

Missing value X (A:B = C:X) for different values of B
B	Missing value X (A:B = C:X)
2	8
3	12
4start	16
6	24
8	32

Missing value X (A:B = C:X) by c

If c goes from 12 to 18, missing value x (A:B = C:X) changes from 16 to 24 (+50%).

Missing value X (A:B = C:X) for different values of C
C	Missing value X (A:B = C:X)
6	8
9	12
12start	16
18	24
24	32

MATH GUIDE

A quick guide to Ratio Calculator

Solve A:B = C:X, find the missing value of a ratio and see it as a decimal and a percentage. Use it to get an accurate missing value x (A:B = C:X) in seconds — free, with no sign-up.

Instant results
See your missing value x (A:B = C:X) the moment you enter your numbers.
Free, no sign-up
Every calculator here is free to use, with no account required.
Accurate & transparent
The same standard formula runs on our server for every calculation.

How to Use the Ratio Calculator

Enter A

Provide your a.

Enter B

Provide your b.

Enter C

Provide your c.

View Your Results

Get your missing value x (A:B = C:X) instantly, calculated on our server.

What is Ratio Calculator?

Solve A:B = C:X, find the missing value of a ratio and see it as a decimal and a percentage. This math tool works out your missing value x (A:B = C:X) instantly, so you don't have to do the math by hand.

“One quick calculation, so you always know your missing value x (A:B = C:X) before you decide.”

What Affects Your Missing value X (A:B = C:X)

Your missing value x (A:B = C:X) depends on the values below.

A
Changing your a changes your missing value x (A:B = C:X).
B
Changing your b changes your missing value x (A:B = C:X).
C
Changing your c changes your missing value x (A:B = C:X).

Example Result

Here's what you can expect from a ratio calculator calculation:

A: 3
B: 4
C: 12
Missing value X (A:B = C:X): 16
A ÷ B: 0.75
A as a share of A + B: 42.86 %

Frequently Asked Questions

How does a affect missing value x (A:B = C:X)?: If a goes from 3 to 4.5, missing value x (A:B = C:X) changes from 16 to 10.6667 (−33%).
How does b affect missing value x (A:B = C:X)?: If b goes from 4 to 6, missing value x (A:B = C:X) changes from 16 to 24 (+50%).
What is the formula for the Ratio Calculator?: Missing value X (A:B = C:X) = B × C ÷ A; A ÷ B = A ÷ B; A as a share of A + B = A ÷ (A+B) × 100. The calculator applies it to the values you enter and shows the missing value x (A:B = C:X).
How to calculate ratio calculator?: Fill in a, b and c in the Ratio Calculator above and your missing value x (A:B = C:X) is calculated instantly. Change any value to see how the result responds.
What does an example ratio calculator calculation look like?: If a is 3, b is 4 and c is 12, the missing value x (A:B = C:X) is 16, the a ÷ b is 0.75 and the a as a share of a + b is 42.86 %.
What do I need to enter in the Ratio Calculator?: A, B and C. The missing value x (A:B = C:X) updates as soon as you change a value.

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