Reverse lookup: 19 common resolutions
Every row is computed with the same two operations the tool uses: reduce by the greatest common divisor for the exact ratio, and divide width by height for the decimal. "Off by" is the relative distance from the nearest named standard.
| Pixels | Exact ratio | Decimal | Nearest standard | Off by | Usually is |
|---|---|---|---|---|---|
| 1920×1080 | 16:9 | 1.7778 | 16:9 | exact | Full HD video, monitors |
| 3840×2160 | 16:9 | 1.7778 | 16:9 | exact | 4K UHD |
| 2560×1440 | 16:9 | 1.7778 | 16:9 | exact | QHD gaming monitors |
| 1366×768 | 683:384 | 1.7786 | 16:9 | 0.049% | Budget laptop panels |
| 854×480 | 427:240 | 1.7792 | 16:9 | 0.078% | Streaming "480p" |
| 1440×900 | 8:5 | 1.6000 | 16:10 | exact | WXGA+ laptops |
| 2560×1600 | 8:5 | 1.6000 | 16:10 | exact | WQXGA productivity displays |
| 1280×1024 | 5:4 | 1.2500 | 5:4 | exact | Older SXGA monitors |
| 3440×1440 | 43:18 | 2.3889 | 2.39:1 | 0.046% | Ultrawide UW-QHD |
| 2560×1080 | 64:27 | 2.3704 | 2.39:1 | 0.821% | Ultrawide UW-FHD |
| 6000×4000 | 3:2 | 1.5000 | 3:2 | exact | 24 MP camera files |
| 3024×4032 | 3:4 | 0.7500 | 3:4 | exact | Phone photo, portrait |
| 1080×1350 | 4:5 | 0.8000 | 4:5 | exact | Instagram portrait post |
| 1080×1920 | 9:16 | 0.5625 | 9:16 | exact | TikTok / Reels / Shorts |
| 1080×566 | 540:283 | 1.9081 | 1.85:1 | 3.14% | Instagram landscape post |
| 2048×858 | 1024:429 | 2.3869 | 2.39:1 | 0.128% | DCI 2K "scope" cinema |
| 1998×1080 | 37:20 | 1.8500 | 1.85:1 | exact | DCI 2K "flat" cinema |
| 2480×3508 | 620:877 | 0.7070 | 3:4 | 5.74% | A4 page at 300 dpi |
| 1170×2532 | 195:422 | 0.4621 | 9:16 | 17.9% | Tall phone screen |
Worked example: 1366×768, step by step
This is the resolution that makes people distrust ratio calculators, so here is the whole computation. Euclid's algorithm repeatedly replaces the pair (a, b) with (b, a mod b) until the remainder hits zero; the last non-zero divisor is the GCD:
| Step | Division | Remainder |
|---|---|---|
| 1 | 1366 = 1 × 768 + 598 | 598 |
| 2 | 768 = 1 × 598 + 170 | 170 |
| 3 | 598 = 3 × 170 + 88 | 88 |
| 4 | 170 = 1 × 88 + 82 | 82 |
| 5 | 88 = 1 × 82 + 6 | 6 |
| 6 | 82 = 13 × 6 + 4 | 4 |
| 7 | 6 = 1 × 4 + 2 | 2 |
| 8 | 4 = 2 × 2 + 0 | 0 |
The GCD is 2, so 1366×768 reduces to 683:384 — and that is the correct, exact answer. Its decimal is 1.7786 against 16:9's 1.7778, a gap of 0.049%. For comparison, 1920×1080 takes only four steps to reach a GCD of 120 and lands on a clean 16:9. Nothing is wrong with your monitor; the two numbers simply do not share large factors.
Worked example: a tall phone screen
A 1170×2532 phone screen reduces to 195:422, decimal 0.4621. No video standard is close — 9:16 is 0.5625, nearly 18% away, and the tool correctly reports that nothing common is within 2%. Even the marketing label is approximate: exact 19.5:9 at 1170 wide would be 2535 px tall, not 2532, a 0.12% difference. The practical consequence is the interesting part. A 16:9 landscape video held upright fills the width and only 26% of the screen height; a 9:16 vertical video fills the width and about 82% of the height, which is why even "full screen" vertical video is usually letterboxed or slightly cropped on tall phones.
Worked example: a scanned A4 page
A4 scanned at 300 dpi is 2480×3508 px, which reduces to 620:877 — decimal 0.7070 (0.706956 in full). That is not a media ratio at all: ISO 216 paper is built on 1 ÷ √2 ≈ 0.70711, the property that halving an A4 sheet gives two sheets of the same shape. The scan lands a hair off that ideal because 210 mm and 297 mm at 300 dpi work out to 2480.3 and 3507.9 px, and both get rounded to whole pixels — the table shows what the pixels are, not what the standard aims at. The nearest common ratio, 3:4, is 5.7% away, so fitting a scan into any standard photo frame will always visibly letterbox or crop. When the calculator says nothing is within 2%, that is usually the real answer rather than a failure.
How to sanity-check any result by hand
- Divide. Width ÷ height. Above 1 is landscape, below 1 is portrait, exactly 1 is square.
- Compare to the decimal, not the fraction. 683:384 tells you nothing at a glance; 1.7786 versus 1.7778 tells you everything.
- Check divisibility for exactness. For an exact 16:9, the width must divide by 16 and the height by 9. 1366 ÷ 16 = 85.375, so it cannot be exact.
- Treat sub-0.1% gaps as the standard. They come from encoder rounding to even numbers, not from a different format.
Related pages
Once you know the ratio, the main calculator resizes on it without distortion. If the answer came back as 16:9, the 16:9 resolution chart lists every standard size in that family; if it came back near 2.37–2.40, the 21:9 ultrawide page explains why no ultrawide is exactly 21:9. Exporting for vertical feeds instead? See the 9:16 vertical video sizes.