Ratio Calculator
Simplify ratios, scale them and solve for a missing term.
Enter your values
Enter the a you are working with.
Enter the b you are working with.
Enter the c (leave blank to solve) you are working with.
Enter the d (leave blank to solve) you are working with.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Missing value D
- 45
- Simplified ratio
- 2 : 3
- As a decimal
- 0.6667
- As a percentage split
- 40% / 60%
Quick answer
Ratios compare quantities; A:B = C:D means A×D = B×C, which lets you solve for any missing term.
A : B = C : D ⟹ A·D = B·C
At a glance
| What it does | Simplify ratios, scale them and solve for a missing term. |
|---|---|
| Category | Math |
| Inputs needed | A, B, C (leave blank to solve), D (leave blank to solve) |
| Formula | A : B = C : D ⟹ A·D = B·C |
| Cost | Free — no sign-up, no download |
How to use the Ratio Calculator
- 1Enter the two parts of your ratio.
- 2To solve a proportion, fill in one of C or D and leave the other blank.
- 3Read the simplified ratio and missing term.
Inputs explained
- A
- Enter the a you are working with.
- B
- Enter the b you are working with.
- C (leave blank to solve)
- Enter the c (leave blank to solve) you are working with.
- D (leave blank to solve)
- Enter the d (leave blank to solve) you are working with.
Frequently asked questions
How do I scale a recipe ratio?
Multiply both sides by the same factor. 2:3 doubled is 4:6, which is the same ratio in different quantities.
What is a proportion?
A statement that two ratios are equal. Cross-multiplying turns it into a simple equation you can solve.
What do I need to enter into the Ratio Calculator?
Just 4 values: a, b, c (leave blank to solve), d (leave blank to solve). Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Ratio Calculator work out the answer?
Ratios compare quantities; A:B = C:D means A×D = B×C, which lets you solve for any missing term. It applies the formula A : B = C : D ⟹ A·D = B·C and shows the working so you can check each step by hand.
Is the Ratio Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.