Math calculator
Ratio Calculator
Solve proportions, simplify ratios, and scale them with steps.
Quick answer
How do you solve a ratio proportion?
Cross-multiply and divide. For 3 : 4 = 6 : x, multiply 4 × 6 = 24 and divide by 3, so x = 8. To simplify a ratio, divide both numbers by their greatest common factor: 24 : 36 ÷ 12 = 2 : 3.
If A : B = C : D, then A × D = B × C, so D = (B × C) ÷ A. To simplify A : B, divide both parts by their greatest common factor.
⚡ Answer updates as you type · Enter = calculate · Esc = reset
- Write the proportion: 3/4 = 6/8 with D unknown.
- Cross-multiply: A × D = B × C.
- D = (B × C) ÷ A = (4 × 6) ÷ 3 = 8
Solve proportions (A : B = C : D), simplify ratios to lowest terms, and scale ratios for recipes, maps, and aspect ratios — with steps.
About this Ratio Calculator
The Ratio Calculator solves proportions like A : B = C : D, simplifies ratios to lowest terms, and scales ratios up or down. Use it for homework, recipes, map scales, mixing paint or concrete, and screen aspect ratios like 16:9 — every answer shows the cross-multiplication steps.
What you'll need
- • Mode: solve proportion, simplify, or scale
- • Values A, B, C, D (leave the unknown blank)
- • Ratio like 24:36 or 2:4:6
- • Scale factor
How it works
- 1. Pick solve, simplify, or scale.
- 2. Enter three known values or the ratio.
- 3. The calculator cross-multiplies or divides by the GCF.
- 4. Read the answer and the proportion bar.
- 5. Follow the worked steps to check your homework.
Worked example
A recipe uses 2 cups flour for 3 cups water. For 9 cups water: 2 : 3 = x : 9, so x = (2 × 9) ÷ 3 = 6 cups of flour. The ratio 1920 : 1080 simplifies to 16 : 9.
Related searches
Ratio Calculator FAQ
What is the Ratio Calculator?
The Ratio Calculator is a free online tool that helps you solve proportions, simplify ratios, and scale them with steps.
How do I use the Ratio Calculator?
Open the Ratio Calculator, enter the requested values, and review the instant estimate on the page.
Is the Ratio Calculator free?
Yes. The Ratio Calculator is free to use on Fast Online Calculator and does not require an account.
How do you simplify a ratio?
Find the greatest common factor of all parts and divide each part by it. 15 : 25 has a GCF of 5, so it simplifies to 3 : 5.
What is the difference between a ratio and a fraction?
A ratio compares parts to parts (3 boys : 2 girls), while a fraction compares a part to the whole (3/5 of the class are boys). The ratio 3 : 2 means 3/5 and 2/5 of the total.
How do you simplify a ratio with decimals?
Multiply every part by 10, 100, or 1000 to make them whole numbers, then divide by the GCF. 1.5 : 2.5 becomes 15 : 25, then 3 : 5.
What ratio is 1920 × 1080?
1920 : 1080 simplifies to 16 : 9, the standard widescreen aspect ratio, because both numbers divide by 120.
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