Ratio calculator
Solve proportions (a:b = c:x), split a total in a given ratio with a choice of remainder strategies, scale a ratio, and compare any width-to-height ratio against 4:3, 16:9, 21:9 and 1:1.618.
Runs in your browserEvery computation happens in your browser — your data never leaves this device.
Solve the proportion
a : b = c : x, so x = b × c ÷ a.
Split a total in a ratio
Proportions are solved by cross multiplication, totals are split with the largest-remainder method for integer leftovers, and aspect ratios are matched by |width ÷ height − preset|.
| Term | Exact share | Allocated |
|---|---|---|
| 1 | 33.3333 | 34 |
| 2 | 33.3333 | 33 |
| 3 | 33.3333 | 33 |
Aspect ratio comparison
| Preset | Width / height | Width at height 1080 |
|---|---|---|
| 4:3 | 1.3333 | 1440 |
| 1:1.618 | 1.6180 | 1747.44 |
| 16:9 | 1.7778 | 1920 |
| 21:9 | 2.3333 | 2520 |
What this tool does
- Scale a design: a 16:9 layout that is 1920 wide — solve 16:9 = 1920:x and get 1080.
- Split an amount or a count in a ratio: 100 in 1:1:1 becomes 34, 33, 33 with the leftover unit going to the largest remainder, so nothing is lost.
- Compare video and monitor shapes: enter any width and height and see whether 4:3, 16:9, 21:9 or 1:1.618 is closest.
- Check a recipe or a parts list: scale a ratio up to real quantities (16:9 × 120 = 1920:1080) and confirm the conversion.
Example
Input
Proportion: a = 16, b = 9, c = 1920; split: total 100, ratio 1:1:1 (largest remainder); aspect: width 1920, height 1080
Output
x = 1080.0000; allocation 34, 33, 33 (exact shares 33.3333, 33.3333, 33.3333, the leftover unit goes to the first term, unassigned remainder 0); closest common aspect ratio 16:9 (width/height 1.7778, distance 0.000000)
Switching the remainder strategy to "leave unassigned" makes 100 in 1:2:3 give 16, 33, 50 with 1 unassigned; "largest weight" hands the leftover to the biggest share instead.
Frequently asked questions
Can I solve for a position other than x?
Yes. The page focuses on a : b = c : x, and the logic layer also solves by position: with any one of a, b, c or x unknown, cross multiplication a × x = b × c gives the answer, as long as the divisor is a known non-zero term.
What do the remainder strategies do?
"Largest remainder" floors every share and then hands the leftover units to the biggest fractional parts, which is the fairest split (100 in 1:1:1 gives 34, 33, 33). "Largest weight" gives the leftover to the biggest shares, useful when priority follows weight. "Leave unassigned" keeps the floored values and reports the remainder separately.
Why must the total be an integer?
Remainder handling is about indivisible units — whole yuan, boxes, seats. A fractional total makes "floor" and "remainder" ambiguous. If you need fractional shares, convert the total to its smallest unit first (yuan to cents, for example) and split that.
How is the closest aspect ratio decided?
The tool computes width ÷ height and compares it with the four presets (4:3 ≈ 1.3333, 16:9 ≈ 1.7778, 21:9 ≈ 2.3333, 1:1.618 = 1.618) by absolute difference, then reports the smallest one together with that distance. A smaller distance means a closer match.
How is scaling different from simplifying?
Scaling multiplies a simple ratio by a factor to reach real dimensions (16:9 × 120 = 1920:1080); simplifying divides real dimensions down to the simplest ratio (1920:1080 = 16:9). They are inverses — this page scales, and the ratio simplifier reduces.
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