About the Paper Size Converter
Paper comes in several systems. Most of the world uses the ISO A series (A4 is the standard office size), while the US and Canada use Letter and Legal. This tool lists the sizes in millimetres, centimetres and inches, in portrait or landscape, and works out how many pixels that is at a resolution you choose, as well as at 72, 150 and 300 dpi, which is useful for designing and printing. Type the paper size, the orientation and the resolution and the paper sizes appears at once, with a few related figures underneath, and you can copy the result with one tap. The sums run in your browser, so nothing you enter is uploaded.
Updated October 2026
How to use the Paper Size Converter
- 1Enter the paper size, the orientation and the resolution.
- 2Pick the units or options from the menus if the paper sizes tool offers them.
- 3Read the paper sizes in the large result box.
- 4Look at the extra rows for related figures.
- 5Press Copy result to keep the answer.
When you need the paper sizes
Designers use it to set up documents and posters at the right size, photographers to check whether an image is big enough for print, and office workers to understand why a PDF does not fit another country's paper.
Each step in the A series halves the area of the page: two A5 sheets make one A4, and two A4 sheets make an A3. B sizes lie between the A sizes, and C sizes are for envelopes that fit A-sized paper.
How the paper sizes is worked out
Pixels = size in inches × dpi. ISO sizes keep a ratio of 1 : √2, so each size halves to the next when folded. A4 is 210 × 297 mm, which is 8.27 × 11.69 inches. At 300 dpi it is 2,480 × 3,508 pixels, at 150 dpi 1,240 × 1,754 and at 72 dpi 595 × 842. US Letter is 215.9 × 279.4 mm (8.5 × 11 in), a little wider and shorter than A4.
Every answer on this page comes from that one rule, so you can check any result by hand with a calculator. The figures shown underneath, such as other units, are conversions of the same answer.
- 27 paper sizes
- Portrait or landscape
- Pixels at any dpi
Mistakes to avoid with paper sizes
Printers cannot print right to the edge, so leave a margin or add bleed for artwork that runs off the page. The pixel sizes are for the whole sheet. For photos, the Print Size Calculator tells you whether your image has enough pixels for a given print size.
On phone and computer
On a phone, type into the boxes one after another and read the paper sizes underneath; Copy result puts it on the clipboard for a message or a note. On a computer the inputs sit on the left and the answer on the right, so you can change one figure and watch the paper sizes move. The paper size converter works the same on both. If you are printing a picture at one of these sizes, check that it is sharp enough with the PPI Calculator, and compare the shape with the Aspect Ratio Calculator.
Features
- Leave margins and bleed
- ISO sizes halve
- Use 300 dpi for sharp print
- Clear messages when the paper sizes inputs make no sense
- Copy the result with one tap
- Private: nothing is uploaded
Frequently asked questions
How do I calculate paper sizes?
Pixels = size in inches × dpi. ISO sizes keep a ratio of 1 : √2, so each size halves to the next when folded. A4 is 210 × 297 mm, which is 8.27 × 11.69 inches. At 300 dpi it is 2,480 × 3,508 pixels, at 150 dpi 1,240 × 1,754 and at 72 dpi 595 × 842. US Letter is 215.9 × 279.4 mm (8.5 × 11 in), a little wider and shorter than A4.
What is the formula for paper sizes?
Pixels = size in inches × dpi. ISO sizes keep a ratio of 1 : √2, so each size halves to the next when folded. The paper size converter applies it exactly and rounds only the displayed answer to six significant figures.
What size is A4 in inches?
8.27 by 11.69 inches.
What is the difference between A4 and Letter?
A4 is narrower and taller. Letter is 8.5 × 11 inches, about 6 mm wider and 18 mm shorter.
What dpi should I use for print?
300 dpi for sharp photos and text, 150 for posters seen from further away.
Is this paper size converter free and private?
Yes. It is free, needs no account and runs in your browser, so the numbers you type are not uploaded or stored.