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 |
Running Euclid's algorithm on 1366×768
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.
A 1170×2532 phone screen matches no video standard
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.
An A4 page scanned at 300 dpi
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.