Fill any three boxes, the fourth is solved. for 1 : 2 : 4.
Simplified ratio
Decimal (A ÷ B)
1 : x
x : 1
A share
B share
Next steps: Resize an image to this ratio · Crop a PDF to a page size · Aspect Ratio Calculator
The slider rewrites C and D as the simplified A : B pair times the scale — the same engine as the Scale mode.
Enter both values to simplify the ratio.
Greatest common divisor
Decimal (A ÷ B)
A — share of total
B — share of total
| Multiplier | A | B |
|---|
Next steps: Resize an image to this ratio · Crop a PDF to a page size · Aspect Ratio Calculator
Drag the corner of the rectangle to resize it — or type a size. Hold Shift while dragging to snap to common ratios (16:9, 4:3, 3:2, 1:1, 21:9, 9:16).
The visuals need two non-negative values with a total above zero — the numbers above still work for negative or zero pairs.
Ratio 1 simplified
Ratio 2 simplified
Ratio 1 decimal
Ratio 2 decimal
Cross-multiplying is the test: equal products mean equal ratios, and the bigger product belongs to the bigger ratio.
Each bar shows how much of that ratio's whole belongs to A. The ratio whose A takes the bigger share is the larger ratio.
Add the parts (1 + 16 = 17), divide the total by that sum to get one part, then multiply each part back out. The last part absorbs the rounding, so the amounts always add back up to the total exactly.
Next steps: Percentage Calculator · Invoice Generator
| Multiplier | A | B |
|---|
Scaling never changes the ratio itself — every row of this table is the same shape at a different size.
For the current ratio
Ratio
Fraction
Decimal
Percent
500 split 3 : 2
Equal: both simplify to 3 : 4
500 g total at 1 : 16 (coffee to water)
Coffee
Water
Solve: 5 : 8 = 15 : ?
Streak: 0 correct in a row
Type your screen’s resolution in pixels. The reduced ratio is loaded into the Simplify tab as you type, ready to scale or split.
Three ratio jobs in one place: solve a proportion — fill any three of A : B = C : D and the fourth is worked out for you; simplify & visualise a pair with its GCD, shares and charts; or split an amount by a ratio so the parts add back up exactly. Everything updates live, in your browser.
For screen resolutions and resizing — finding the matching height for a target width — use the Aspect Ratio Calculator.
A ratio puts two quantities side by side and states how they measure against each other. It answers the question “for every so many of this, how many of that?” — and, equivalently, how many times one quantity contains the other. If a ward schedules 2 nurses for every 5 patients, the nurse-to-patient ratio is 2:5: in each group of 5 patients there are 2 nurses, and the number of nurses works out at 2/5 — 0.4 — of the number of patients.
The same comparison can be written three ways: with a colon (2:5), with words (2 to 5), or as a fraction (2/5). All three say the same thing, but the order is part of the meaning — 2:5 is not the same statement as 5:2.
Ratios are not limited to pairs. Three or more quantities can be compared at once when they belong together: a bricklayer’s mortar might mix cement, sand and gravel in the ratio 1:2:4, and every batch, large or small, keeps those proportions.
Multiplying or dividing every term by the same number changes nothing — 2:5, 4:10 and 200:500 are the same ratio wearing bigger numbers. That is why a ratio can always be reduced to its simplest form by dividing every term by their greatest common divisor, exactly the way a fraction is reduced: 12:18 becomes 2:3 after dividing both terms by 6.
Worked example. A class of 25 students has boys and girls in the ratio 3:2. The ratio has 3 + 2 = 5 parts altogether, so one part is 25 ÷ 5 = 5 students. That gives 3 × 5 = 15 boys and 2 × 5 = 10 girls — and 15 + 10 = 25, the whole class. Splitting a total this way is exactly what the Split by ratio tab above does with any numbers.
An aspect ratio describes the shape of a screen or image: its width compared with its height, reduced to the simplest whole numbers. A 1920 × 1080 display is 16:9 because both measurements divide by 120 — and a 3840×2160 4K screen has exactly the same 16:9 shape at four times the pixel count. The table below lists the resolutions screens are commonly made in, under the names the industry gives them — handy when you are picking an export size, checking what a “1080p” claim really means, or feeding matching numbers into the calculator above.
Tip: click any row to load that ratio into the calculator above.
| Name | Aspect ratio | Width (px) | Height (px) | Preview |
|---|---|---|---|---|
| 480p | 3:2 | 720 | 480 | 480p3:2 |
| 576p | 5:4 | 720 | 576 | 576p5:4 |
| 720p | 16:9 | 1280 | 720 | 720p16:9 |
| 1080p | 16:9 | 1920 | 1080 | 1080p16:9 |
| 2160p (4K UHD) | 16:9 | 3840 | 2160 | 2160p (4K UHD)16:9 |
| 4320p (8K UHD) | 16:9 | 7680 | 4320 | 4320p (8K UHD)16:9 |
| 8640p | 16:9 | 15360 | 8640 | 8640p16:9 |
| SVGA | 4:3 | 800 | 600 | SVGA4:3 |
| WSVGA | ~17:10 | 1024 | 600 | WSVGA~17:10 |
| XGA | 4:3 | 1024 | 768 | XGA4:3 |
| XGA+ | 4:3 | 1152 | 864 | XGA+4:3 |
| WXGA | 16:9 | 1280 | 720 | WXGA16:9 |
| WXGA | 5:3 | 1280 | 768 | WXGA5:3 |
| WXGA | 16:10 | 1280 | 800 | WXGA16:10 |
| SXGA (UVGA) | 4:3 | 1280 | 960 | SXGA (UVGA)4:3 |
| SXGA | 5:4 | 1280 | 1024 | SXGA5:4 |
| HD | ~16:9 | 1360 | 768 | HD~16:9 |
| HD | ~16:9 | 1366 | 768 | HD~16:9 |
| SXGA+ | 4:3 | 1400 | 1050 | SXGA+4:3 |
| WXGA+ | 16:10 | 1440 | 900 | WXGA+16:10 |
| HD+ | 16:9 | 1600 | 900 | HD+16:9 |
| UXGA | 4:3 | 1600 | 1200 | UXGA4:3 |
| WSXGA+ | 16:10 | 1680 | 1050 | WSXGA+16:10 |
| FHD | 16:9 | 1920 | 1080 | FHD16:9 |
| WUXGA | 16:10 | 1920 | 1200 | WUXGA16:10 |
| QWXGA | 16:9 | 2048 | 1152 | QWXGA16:9 |
| WQHD | 16:9 | 2560 | 1440 | WQHD16:9 |
| WQXGA | 16:10 | 2560 | 1600 | WQXGA16:10 |
Resizing one of these to a new width? The Aspect Ratio Calculator works out the matching height for you.
Proportions, scaling, simplifying and fair splits — every ratio job, answered live as you type.
100% free · No sign-up · No daily limits · No watermarks · Processed in your browser — files never leave your device
Solve any proportion (A : B = C : D), simplify ratios with live pie and bar visuals, find your screen's ratio, and split any amount by a ratio — free.
A picture printed 3:4 at 600 pixels wide must be 800 pixels tall: 3 : 4 = 600 : 800. The calculator finds the missing term by cross-multiplication (4 × 600 ÷ 3), reports the pair simplified as 3:4, rewritten as 1 : 1.333 and as 0.75 : 1, and as shares of the whole — 3/7 = 42.857% and 4/7 = 57.143%. The same screen simplifies 12:18 to 2:3 by dividing both terms by their greatest common divisor, 6.
A proportion A : B = C : D holds exactly when the cross-products match (A × D = B × C), so a missing term is the product of the two terms on the other diagonal divided by the term opposite it. Simplification scales decimal inputs up to whole numbers, divides both terms by their greatest common divisor, then scales back — the same reduction used for fractions. Percentage shares are each term's portion of the pair's total. The split works in the smallest displayed unit and gives any rounding leftover to the final part, so the rounded shares always add back to the entered total.
Fill in the other three values in the Proportion solver and leave the one you need blank. The tool cross-multiplies: in A : B = C : D the missing D is B × C ÷ A, and every position follows the same rule. The solved value is highlighted and written into its box, so you can carry on editing around it.
Open Split by ratio, enter the amount as the total and the two parts of the ratio — for example, 500 split 3:2 gives 300 and 200. Each share appears with its percentage. Shares are rounded to the total's decimal places and the final part absorbs the rounding, so the parts always add back up to the total exactly — no lost cents.
It means dividing both terms by their greatest common divisor so the relationship is written with the smallest whole numbers that express it: 12:18 simplifies to 2:3. Decimal ratios are scaled to whole numbers first, so 1.5:2.5 simplifies to 3:5 with a common divisor of 0.5.
They are unit ratios — the same comparison rewritten with one side set to 1. A ratio of 3:4 is 1 : 1.333 (for every 1 of A there are 1.333 of B) and 0.75 : 1 (A is 0.75 of B). Unit ratios are the natural form for unit prices, exchange rates and per-one comparisons.
Yes. The solver and the simplifier both accept decimals, and negative values solve and simplify correctly. The pie, bar and rectangle visuals only draw for non-negative pairs — a negative slice has no picture — while the numbers keep updating. Splitting expects a non-negative total and non-negative parts.
This calculator works with the ratio itself: solving proportions, simplifying pairs and splitting amounts. The Aspect Ratio Calculator is specialised for screens and images — give it dimensions and a target width and it finds the matching height and the standard format (16:9, 4:3 and friends) your numbers belong to.
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