Ratio Reference Table
| Ratio | What it is | Anchor you can check |
|---|---|---|
| 16:9 | HDTV and online video | 1920×1080, 3840×2160 |
| 9:16 | Vertical short video | 1080×1920 |
| 1:1 | Square social posts | 1080×1080 |
| 4:3 | Classic TV, older tablets | 1024×768 |
| 64:27 | Ultrawide, marketed as "21:9" | 2560×1080 = 2.370, not 2.333 |
| 3:2 | Large laptops and tablets | 3000×2000 |
| 1:1.5 | White rice to water | 1 cup rice + 1.5 cups water |
| 1:15–1:18 | Coffee grounds to water | 30 g grounds + 450–540 g water |
| 1:2 | Espresso yield | 18 g in → 36 g out |
| 3:1 | Vinaigrette oil to vinegar | 45 ml oil + 15 ml vinegar |
| 50:1 | Two-stroke gas to oil | 100 ml oil per 5 L gas |
| 1:4 | Compost greens to browns | 1 bucket scraps + 4 buckets dry leaves |
| 1.618:1 | Golden ratio, (1+√5)/2 | 1.6180339887… |
| 1:24,000 | USGS 7.5-minute topo maps | 1 inch = 2,000 feet |
| 1:64 | Die-cast toy cars | the ~3-inch Hot Wheels size |
| 1:87 | HO scale model trains | European standard gauge sizing |
| 28% / 36% | Housing vs total debt income caps | $7,000 monthly → $1,960 / $2,520 |
A ratio is a recipe, and most ratio charts stop at the recipe. The difference between 16:9 that means something and 16:9 that just looks technical is an anchor: 1920 by 1080 pixels, 100 ml of oil in 5 liters of gas, 1 inch on the map being 2,000 feet on the ground. Every row below carries its anchor, so you can verify the math instead of trusting the chart.
The three groups cover the places ratios actually bite: screens and video, where the wrong ratio means stretched faces; the kitchen and garage, where the wrong ratio means mush or a seized piston; and the reference numbers — golden ratio, map scales, model scales, the 28/36 housing rule — that come up in arguments and deserve exact values.
How to use
- Pick the group you need, or filter with the chips above the tables; the filter remembers your last choice for next visit.
- Read the anchor column as the worked instance of the ratio — resolutions for screens, grams and milliliters for the kitchen, dollars for the housing rule.
- When a ratio here needs adjusting to your own numbers, the ratio calculator solves it, and the topic tools (coffee, compost, aspect) go deeper on their single subject.
Worked examples
Simplifying 120:60 with the greatest common divisor
Both numbers divide by 60, so 120:60 reduces to 2:1. A slower one: 102:36 — GCD of 102 and 36 is 6, giving 17:6. The test is divisibility, not vibes: if you cannot name a common factor, try primes 2, 3, 5, 7 in order and stop at the square root of the smaller number.
The 1:2 trap — which share is which
A 1:2 dilution concentrate-to-water means one part concentrate to two parts water: the concentrate is one third of the final mix, not half. That is why 1 cup of concentrate plus 2 cups of water fills three cups, and why 'a 50% mix' is a different claim than 'a 1:2 mix'. Percentages divide by the total; ratios divide by the other part.
The 50:1 fuel run, computed both directions
5 liters of gasoline at 50:1 needs 5,000 / 50 = 100 ml of two-stroke oil. Working the other way from the oil bottle: 100 ml of oil supports 50 x 100 = 5,000 ml of gas. The reciprocal move is the useful one at the pump — oil in hand fixes the gas you can buy.
Frequently asked questions
How do I simplify a ratio like 120:60?
Divide both sides by their greatest common divisor: GCD(120, 60) = 60, so the ratio simplifies to 2:1. For 102:36, the GCD is 6 and the clean form is 17:6. A ratio is fully simplified when no number above 1 divides both sides — checking 2, 3, and 5 first catches most cases.
Is a 1:2 ratio the same as 50 percent?
No, and the confusion runs both ways. In 1:2, the first component is 1 part out of 3 total — about 33 percent of the mix. Saying 50 percent means one component is half of the total, which as a ratio is 1:1. Ratios compare part to part; percentages compare part to whole. The 3 cups result in the worked example above is the fastest way to feel the difference.
Why do two-stroke engines need fuel mixed at 50:1?
A two-stroke engine has no oil sump — the crankshaft and piston are lubricated only by oil carried through with the fuel, so the oil must ride in the gasoline and burn with it. 50:1 means 100 ml of oil per 5 liters of gas. Too little oil and the piston scores within minutes; too much and it fouls plugs and smokes. Modern synthetic oils let manufacturers lean the mix from the older 25:1 or 32:1 standards.
What makes the golden ratio golden?
Algebra, not aesthetics: φ = (1 + √5)/2 ≈ 1.618 is the unique positive number where φ² = φ + 1 — the only ratio such that removing a square from a φ-rectangle leaves a smaller φ-rectangle. The repeat-in-self property is the mathematical content. The famous art-historical claims are mostly retrospective pattern-matching; the checkable appearances are pentagons, Fibonacci limits, and continued fractions.
Is my monitor really 21:9, or is that a marketing number?
Marketing shorthand. A 2560×1080 ultrawide is 2560/1080 = 2.370, which as an integer ratio is 64:27 — about 21.33:9, so '21:9' rounds it down. True 21:9 would be 2.333, e.g. 2520×1080. The same rounding applies to '12:9' phones that are really 4:3 stretched by naming. Read the resolution and divide; the pixel numbers never round.