RatioLab

Ratio Calculator

a : b as a decimal, as a percentage — all at once.

As decimal

1.5

a : b: 6 : 4
As percentage: 150

What you entered

a: 6b: 4

1
Express as a fraction
6 ÷ 4= 1.5
2
Convert to a percentage
1.5 × 100= 150%

Result

As decimal: 1.5

6 : 4 simplifies to a decimal ratio of 1.5, or 150%.

Ratios as decimals and percentages

A ratio a to b expressed as a decimal is a divided by b, and as a percentage that decimal times 100.

Ratio	Decimal	Percentage
1 : 4	0.2500	25.00
2 : 5	0.4000	40.00
1 : 2	0.5000	50.00
7 : 10	0.7000	70.00
3 : 4	0.7500	75.00
16 : 9	1.7778	177.78

The last row is the widescreen aspect ratio, and it shows what happens when the first term is larger - the decimal exceeds 1 and the percentage exceeds 100. Be careful about the distinction between a ratio and a fraction of a whole: a ratio of 1:4 means one part to four parts, so it is one fifth of the total, not one quarter, even though the decimal reads 0.25. That ambiguity is the most common mistake in mixing paint, concrete or drinks by ratio.

A comparison, not just a fraction

A ratio compares two quantities directly — a:b is simply a divided by b, which can then be read as a decimal or converted to a percentage for easier comparison.

Common real-world ratios

Recipe scaling, aspect ratios for screens and photos, and mixing ratios for paint or concrete are all everyday applications of the same underlying idea.

Frequently asked questions

How do I simplify a ratio?

Divide both numbers by their GCD. 12:8 → divide both by 4 → 3:2. For 15:25 → divide by 5 → 3:5. A simplified ratio has no common factors — the same idea as simplifying a fraction.

How do I convert a ratio to a percentage?

Divide the first number by the second and multiply by 100. 3:4 = 3÷4 = 0.75 = 75%. For a parts ratio like 2:3, the first is 2/5 = 40% and the second is 3/5 = 60% of the total.

What is an aspect ratio?

An aspect ratio describes a shape's proportions — width:height. Common screen ratios: 16:9 (widescreen TV), 4:3 (old TV), 21:9 (ultrawide). Photo ratios: 3:2 (DSLR), 4:3 (phone), 1:1 (square/Instagram).