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Photo Dimensions Calculator

Convert pixels, inches, cm and mm at any DPI — and see how big your photo can print.

Runs in your browserNo sign-up requiredNo watermark
I know the size in

DPI decides how big these pixels print. It doesn't change the image file itself.

Pixels1,800 × 1,200 px
Inches6 × 4 in
Centimetres15.24 × 10.16 cm
Millimetres152.4 × 101.6 mm
Aspect ratio
3:2
Megapixels
2.2 MP
Orientation
Landscape
Largest sharp print: 6 × 4 in (15.24 × 10.16 cm) at 300 DPI. At 150 DPI, fine for posters seen from a distance: 12 × 8 in.

Photo prints

ID & passport

Screens & social

What Is This Calculator For?

Photo size requirements come in different units depending on where you're submitting — passport applications in inches or cm, social media in pixels, print shops in a mix of both. This calculator converts between all of them instantly, using a DPI value to bridge pixel dimensions and physical size, plus a set of built-in presets for the sizes people look up most often. It's a pure math tool — no image is uploaded or processed here, just the conversion itself.

How to Use This Calculator

  1. 1Enter a size, or read it from a photoType the width and height in the unit you know, or pick a photo to use its exact pixel size.
  2. 2Set the DPI300 DPI is the standard for sharp photo prints. Tap a common value or type your own.
  3. 3Read every unit at oncePixels, inches, centimetres and millimetres update as you type, with a copy button for each.
  4. 4Check print size and qualitySee the largest sharp print a photo allows, or how many pixels a print size needs.

Why DPI Actually Matters

  1. 1The same pixel grid, printed two different sizesA 1200×1200px image at 300 DPI prints as a 4×4 inch photo. The exact same file at 150 DPI prints as an 8×8 inch photo — twice as large, but noticeably softer, since each printed inch now has half as many dots of detail.
  2. 2Screens don't really "have" a DPI in the same senseA screen just displays pixels 1:1 (roughly) regardless of DPI metadata in the file — this is why DPI is largely irrelevant for anything that will only ever be viewed on a screen, and only matters once physical printing enters the picture.
  3. 3Print shops and official forms specify DPI for a reasonA photo lab or a passport office cares about DPI because it guarantees the print or scan will meet a minimum sharpness standard at the required physical size — which is why document photo requirements typically state both a physical size and a DPI together.

Good to Know

  • DPI (dots per inch) is what links pixels to physical size — a 300×300px image is 1×1 inch at 300 DPI, but 3×3 inches at 100 DPI.
  • 300 DPI is the standard for high-quality printing; 72–96 DPI is typical for screens, though pixel dimensions matter more than DPI for anything web-only.
  • Passport and ID photo requirements vary by country — always double-check the exact requirement for your specific application before submitting.
  • This is a calculator only — pair it with the Image Resizer to actually resize a photo to the dimensions you calculate here, or the Passport / ID Photo Maker for document-specific presets with built-in cropping.

Frequently Asked Questions

Why do pixels need a DPI to convert to inches or cm?

A pixel by itself has no physical size — it only gets one when you specify a resolution (DPI). The same pixel dimensions can be a tiny postage stamp or a large poster depending on the DPI used to print it.

What DPI should I use for a passport or ID photo?

Most photo ID requirements specify a DPI (often 300) alongside the physical size — check the specific requirement for your document, since it varies by country and document type.

Does this tool actually resize my photo?

No — it's a calculator for figuring out the right dimensions. Once you know the pixel size you need, use the Image Resizer to actually resize your photo to it, or the Passport / ID Photo Maker if you also need to crop to that exact document ratio.

What DPI is right for web and social media images?

For screens, DPI is effectively meaningless — what matters is the pixel dimensions themselves. A 1080×1080px image displays the same on screen whether its metadata says 72 DPI or 300 DPI.

How do I know what physical size my printed photo will actually be?

Divide your pixel width by your intended DPI — a 3000px-wide image printed at 300 DPI comes out 10 inches wide (3000 ÷ 300). This calculator does that math for you instantly across all four units.

How do I find the dimensions of my photo?

Tap "Read size from a photo" and choose the image — the calculator fills in its exact pixel width and height (the photo stays on your device). You then see it in inches, cm and mm at your chosen DPI, plus its aspect ratio and megapixels.

How many pixels do I need for a 4×6 inch print?

At 300 DPI, a 4×6 inch print needs 1200 × 1800 pixels. For 5×7 inches it's 1500 × 2100, and for 8×10 inches 2400 × 3000. Pick a print size from the presets to see any of these instantly.

Is this tool free to use?

Yes, completely free with no sign-up, and it runs entirely in your browser.