Standard photo print sizes: inches, centimetres and the megapixels each one needs
Photo print sizes are a de-facto standard set: labs everywhere offer the same ladder from wallet and 4×6 up to 24×36 and beyond. This chart gives each size in inches and exact centimetres (1 inch = 2.54 cm by definition), plus the pixel dimensions published by two real labs — mPix's official upload chart and Nations Photo Lab's resolution guide — so you can see both the minimum a lab will happily print and the optimum it aims for. Want your own numbers instead? The DPI calculator does the arithmetic for any size.
Key takeaways
- A 4×6 print needs just 1200 × 1800 px (2.2 MP) at 300 PPI — every camera and phone sold today clears it.
- mPix's official chart lists optimum pixels at exactly 250 PPI and minimums at 100 PPI; Nations lists 125 / 180 / 300 PPI columns.
- The big jumps: 16×20 needs ~29 MP at 300 PPI but only ~13.5 MP at 200 and ~7.2 MP at 150.
- US photo sizes (4×6, 8×10…) are not ISO A-series paper sizes — A4 is 8.3 × 11.7 in, so printing A4 needs its own numbers.
The standard sizes chart (inch / cm / pixels)
Pixel columns are transcribed from the labs' published charts and cross-check the arithmetic exactly: mPix optimal = 250 PPI, mPix minimum = 100 PPI, Nations minimum = 125 PPI, and the classic 300 PPI target = inches × 300.
| Print size | Centimetres | 300 PPI (classic target) | 250 PPI (mPix optimal) | 125 PPI (Nations min) | 100 PPI (mPix min) |
|---|---|---|---|---|---|
| 4 × 6 in | 10.2 × 15.2 | 1200 × 1800 · 2.2 MP | 1000 × 1500 · 1.5 MP | 500 × 750 | 400 × 600 |
| 5 × 7 in | 12.7 × 17.8 | 1500 × 2100 · 3.2 MP | 1250 × 1750 · 2.2 MP | 625 × 875 | 500 × 700 |
| 8 × 10 in | 20.3 × 25.4 | 2400 × 3000 · 7.2 MP | 2000 × 2500 · 5 MP | 1000 × 1250 | 800 × 1000 |
| 8 × 12 in | 20.3 × 30.5 | 2400 × 3600 · 8.6 MP | 2000 × 3000 · 6 MP | 1000 × 1500 | 800 × 1200 |
| 11 × 14 in | 27.9 × 35.6 | 3300 × 4200 · 13.9 MP | 2750 × 3500 · 9.6 MP | 1375 × 1750 | 1100 × 1400 |
| 12 × 18 in | 30.5 × 45.7 | 3600 × 5400 · 19.4 MP | 3000 × 4500 · 13.5 MP | 1500 × 2250 | 1200 × 1800 |
| 16 × 20 in | 40.6 × 50.8 | 4800 × 6000 · 28.8 MP | 4000 × 5000 · 20 MP | 2000 × 2500 | 1600 × 2000 |
| 20 × 30 in | 50.8 × 76.2 | 6000 × 9000 · 54 MP | 5000 × 7500 · 37.5 MP | 2500 × 3750 | 2000 × 3000 |
| 24 × 36 in | 61.0 × 91.4 | 7200 × 10800 · 77.8 MP | 6000 × 9000 · 54 MP | 3000 × 4500 | 2400 × 3600 |
Sources: mPix "Requirements to upload your photos" and Nations Photo Lab "Image Resolution Guidelines" (both official pages, verified 2026-11-16). MP values rounded to one decimal.
Reading the chart honestly
The four pixel columns are not four levels of "correct". They are published answers to different questions. The 300 PPI column is the classic target — WHCC asks for files "as close to the desired print size as possible when it's at 300ppi", and it's the number offset printing standardized on (see where 300 PPI comes from). The 250 PPI column is what mPix actually lists as optimal for its printers. The 125 and 100 PPI columns are lab minimums: files at or above them print without warnings, though detail is visibly softer up close — that trade-off is mapped in the DPI quality ladder.
Which column should you aim for? If the print will be held in hand, use 300 or 250. If it hangs on a wall and gets viewed from a metre or two, 200 or even 150 is a perfectly defensible target — large-format guidance drops fast with distance, as covered in viewing distance & DPI. Nothing on this page is physics; it's what the labs themselves publish, and labs differ.
Square and Panoramic sizes labs actually offer
The standard ladder isn't only rectangles. mPix's chart also lists square formats (4×4, 5×5, 8×8, 10×10, 12×12, 20×20) and panoramics (5×15, 5×30, 10×20, 10×30, 12×24, 12×36). The arithmetic is identical: multiply inches by your target PPI. A 12×12 at 250 PPI is 3000 × 3000 px (9 MP); a 12×36 at 125 PPI needs 1500 × 4500. Panoramics punish low pixel counts fast because one dimension is huge — check any panorama in the calculator before ordering.
Photo sizes vs paper sizes: A-series and US Letter
Photo print sizes are a lab convention, distinct from office paper standards. ISO 216:2007 — the international standard "Writing paper and certain classes of printed matter — Trimmed sizes — A and B series" — defines the A-series on a 1:√2 ratio with A0 at exactly 841 × 1189 mm: A4 is 210 × 297 mm (8.3 × 11.7 in), A3 is 297 × 420 mm (11.7 × 16.5 in). The US and Canada instead use Letter (8.5 × 11 in), Legal (8.5 × 14) and Tabloid (11 × 17). If you print a photo borderless on A4, you need at least 2480 × 3508 px at 300 PPI (8.7 MP) — awkwardly between the 8×10 and 8×12 photo sizes, and its 1:1.41 ratio is narrower than the 1:1.5 of a 3:2 sensor, so cropping applies (see aspect ratios & cropping math).
Wallet sizes
Wallets are the smallest tier and the least standardized — mPix splits them into mini (2.5 × 3.5 in optimum 438 × 625 px) and standard wallets (250 × 350 minimum, 625 × 875 optimal), while Nations lists mini, standard and die-cut wallets with slightly different trims. Any photo that covers a 4×6 covers every wallet format; at these sizes even 150 PPI looks flawless because the print is rarely examined closely.
Photo-print service (concept pick)
Placeholder affiliate card for a consumer lab that prints from ~100 PPI minimums up to archival large formats — matched to the chart above.
Check price →One caveat that isn't about pixels
Resolution only says how many pixels land per inch — not whether they're good pixels. Nations' guide notes its own chart "alone do[es] not guarantee a high quality print": focus, lighting, digital zoom and heavy cropping all matter. A tack-sharp 180 PPI file often beats a mushy 300 PPI one.