How do you simplify a ratio?

Divide every part of the ratio by their greatest common factor (GCF). For example, 12:18 has a GCF of 6, so it simplifies to 2:3.

What is the formula for solving a proportion?

Use cross-multiplication: in a:b = c:d, the product of the means equals the product of the extremes (b × c = a × d). Rearrange to solve for whichever term is unknown.

How do I split a number by a ratio?

Add the ratio parts to find the total number of shares, divide the amount by that total to find the value of one share, then multiply by each ratio part.

What is a 3-part ratio and how is it simplified?

A 3-part ratio compares three quantities, like 1:2:3 for a concrete mix. It's simplified the same way as a 2-part ratio, by dividing all three parts by their greatest common factor.

What's the difference between a ratio and a proportion?

A ratio compares two or more quantities, like 3:4. A proportion is a statement that two ratios are equal, like 3:4 = 6:8.

How do you know if two ratios are equivalent?

Cross-multiply: for a:b and c:d, they are equivalent if a × d equals b × c. You can also simplify both ratios to lowest terms and check if they match.

Ratio Calculator – Simplify, Solve Proportions & Convert to Percent (Free)

📐 Ratio Calculator

Ratio Parts (leave C blank for a 2-part ratio)

Quick Examples

12 : 18 2 : 6 1 : 2 : 3 (concrete mix) 16 : 9 (aspect ratio)

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Enter your values and click Calculate

Your simplified ratio, percentages, and step-by-step work will appear here.

Calculating…

How It Works

Ratio, Proportion & Percentage Formulas Explained

Every mode above reduces to one of these three simple formulas.

Simplify a Ratio

A:B → (A÷GCF):(B÷GCF)

Divide every part by the greatest common factor (GCF) of all parts.

Solve a Proportion

A:B = C:D → A × D = B × C

The product of the means equals the product of the extremes — rearrange to solve for the unknown term.

Ratio → Percentage

Part ÷ Total × 100

Add all parts to get the total, then divide each part by the total and multiply by 100.

Split a Total by Ratio

Share = Total × (Part ÷ Sum of Parts)

Find the value of one "share" by dividing the total by the sum of ratio parts, then multiply by each part.

Worked Example: Simplify 12:18

Find the greatest common factor of 12 and 18: GCF = 6

Divide both parts by 6: 12 ÷ 6 = 2, 18 ÷ 6 = 3

✓ 12:18 simplifies to 2:3 — which is 40% : 60% of the whole

Quick Reference

Common Ratios as Percentages & Decimals

A few frequently searched ratio-to-percentage conversions.

Ratio	Simplified	Part A %	Part B %	Decimal (A÷B)
1:1	1:1	50%	50%	1.0
1:2	1:2	33.33%	66.67%	0.5
1:3	1:3	25%	75%	0.33
2:3	2:3	40%	60%	0.67
3:4	3:4	42.86%	57.14%	0.75
16:9	16:9	64%	36%	1.78
10:5	2:1	66.67%	33.33%	2.0

Everyday Uses

Where Ratio Calculations Show Up

Scaling a Recipe

If a recipe uses a 1:2.5:6.5 ratio of macaroni, milk, and cheese and you want to triple it, use Split by Ratio (or scale each part by the multiplier) to find you'll need 3 boxes of macaroni, 7.5 cups of milk, and 19.5 cups of cheese.

Splitting Costs or Profits

Partners splitting a $3,000 profit in a 2:1 ratio would use Split by Ratio: total shares = 3, one share = $1,000, so the split is $2,000 : $1,000.

Mixing Materials

A 1:2:3 cement mix (cement:sand:gravel) can be scaled to any batch size with Split by Ratio — enter your total volume and the 1:2:3 parts to get exact quantities.

Aspect Ratios

Photo and video aspect ratios like 16:9 or 4:3 are just ratios — Simplify mode confirms they're already in lowest terms, and the percentage breakdown shows the relative width-to-height split.

FAQ

Ratio Calculator — Frequently Asked Questions

Common questions about simplifying, solving, splitting, and converting ratios.