Print is the one place a wrong number actually costs money. On screen you upload the wrong size and you re-upload, no harm done. At the printer you find out your 4x6 was built at 72 DPI when the proof shows up looking like a screenshot of a screenshot, and now you're paying for a reprint and waiting another three days. I've done that. So I built the version of this I actually wanted: pick a size, pick your DPI, add bleed, copy the pixel dimensions straight into your canvas.
The reason print trips people up is that a print size isn't a pixel size. It's a physical size, inches or millimeters, and the pixels depend entirely on how many you pack into each inch. That number is DPI, dots per inch. A 4x6 photo at 300 DPI is 1200 x 1800 pixels. The same 4x6 at 72 DPI is 288 x 432, which looks fine on your monitor and falls apart the second it hits paper. The physical size never changed. The resolution did.
Then there's bleed, which is the part nobody tells you about until your business cards come back with a thin white sliver on one edge. Pick a size below, set your DPI and bleed, and the tool does the multiplication for you across about 79 print sizes.
DPI: why 300 is the print standard
DPI is how many pixels live inside one printed inch. More pixels per inch means a sharper print, up to the point where your eye can't tell anymore. For anything you hold in your hand and read up close, that point is right around 300 DPI. That's the number commercial printers ask for, and it's the number I default to for photo prints, business cards, postcards, flyers, brochures, books, and anything letter-sized.
The math is the same every time. Pixels equal inches times DPI. US Letter at 8.5 x 11 inches becomes 2550 x 3300 at 300 DPI. A4 at 210 x 297 millimeters works out to roughly 2480 x 3508, since you convert the millimeters to inches first (25.4 mm per inch) and then multiply. A standard US business card at 3.5 x 2 inches is 1050 x 600. None of these are numbers you should be memorizing. They're just inches times 300.
The exception is large format. A 24 x 36 poster on a wall, a retractable banner at a trade show, a 4 x 8 foot vinyl sign, those get viewed from a few feet back, sometimes across a room. Your eye can't resolve 300 DPI at that distance, so building a 4 x 8 banner at 300 DPI would mean a 14,400 x 28,800 pixel file that crashes your machine for no visible benefit. For large format, 150 DPI is plenty, and for the biggest banners viewed from far away you can drop lower. The tool lets you flip between 72, 150, 300, and 600 so you can match the DPI to how close someone actually stands.
Bleed: why 0.125 inch saves your edges
Bleed is extra art that extends past the line where the paper gets cut. Cutting machines aren't perfect, they drift a hair one way or the other, so if your background color stops exactly at the trim line, a tiny misalignment leaves a white edge. Bleed fixes that by running your background past the cut, so even when the blade lands a little off, it's still cutting through your design instead of past it.
The US commercial standard is 0.125 inch of bleed on every side. At 300 DPI that's 37.5 pixels per edge, so a 4x6 photo card with bleed becomes 1200 + 75 wide and 1800 + 75 tall, which is 1275 x 1875. The tool adds it on all four sides automatically when you pick a bleed amount, so you don't have to do that addition in your head while you're trying to design.
Large format wants more room because the cutting tolerance on a big vinyl banner is looser than on a stack of business cards. There the standard jumps to 0.25 inch, and the size data already knows that, so banners default to the wider bleed. There's also a safe margin to think about, which is the opposite idea: keep your important stuff, text and logos and faces, pulled in about 0.125 to 0.25 inch from the trim line so nothing critical lands in the zone that might get clipped. Bleed protects the edge of your background. The safe margin protects the middle of your message.
“Bleed protects the edge of your background. The safe margin protects the middle of your message. Set both before you design, not after the proof comes back wrong.
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The print sizes that cover most jobs
There's a long list in the tool, but most jobs land in a handful of families. Here are the anchors.
Photo prints. The 4x6 is the most common print on earth, 1200 x 1800 at 300 DPI. From there the standard ladder runs 5x7, 8x10, 8.5x11, 11x14, 16x20, and up to gallery sizes like 20x30 and 24x36. They're all just inches times your DPI, and most have a 2:3 or close aspect ratio, which is why a 4x6 and a 24x36 both feel like a photo and a 5x7 feels a little squarer.
US paper, the ANSI sizes. US Letter at 8.5 x 11 is ANSI A, the one your office printer assumes. Legal is 8.5 x 14, Tabloid (also called Ledger) is 11 x 17 and that's ANSI B, then it scales up through ANSI C and D for engineering drawings. Half-Letter at 5.5 x 8.5 is the one to know for booklets and zines.
Business cards. US standard is 3.5 x 2 inches, which is 1050 x 600 at 300 DPI. The European card is a touch narrower and taller at 85 x 55 mm, the Japanese standard is 91 x 55 mm, and if you want to stand out there's a square 2.5 x 2.5 and the tiny Moo mini at 2.75 x 1.125. Whatever you pick, build it with the 0.125 bleed, because a business card with a white sliver on one edge reads as cheap even when nothing else is.
Postcards. USPS rules matter here. A First-Class postcard runs from 4x6 at the minimum up to 4.25x6 at the max, and going over that bumps you into letter postage rates. The 5x7 and 6x9 sizes mail fine, they just cost more to send. The tool notes the USPS limits right on the relevant sizes so you don't design something that quietly doubles your mailing cost.
ISO A-series and B-series. This is the rest of the world's paper system, and it's mathematically clean in a way the US sizes aren't. A4 (210 x 297 mm) is the international Letter. Every step folds in half to the next: A4 halves into A5, A5 into A6, and so on up to the huge A0 at 841 x 1189 mm. The whole series holds the same aspect ratio (a 1:1.414 rectangle, the square root of 2) so anything designed for A4 scales perfectly to A3 or A5 with no reflow. The B-series sits between the A sizes for posters and books.
Posters. The everyday sizes are 18x24, 24x36, and 27x40 (the US movie one-sheet). At 150 DPI a 24x36 poster is 3600 x 5400 pixels, which is a sane file size for something you'll view from a few feet away. Push it to 300 if it's going somewhere people lean in close, but for a wall, 150 holds up.
Envelopes. The #10 at 9.5 x 4.125 inches is the business standard, the one your invoices come in. The A-series envelopes (A2, A6, A7) are the ones for invitations and cards, sized to fit folded stationery.
Book and trade. The most common US trade paperback is 6 x 9. Mass-market paperbacks are smaller at 4.25 x 6.87, digest is 5.5 x 8.5, and there's a ladder of trade sizes in between depending on your print-on-demand vendor's spec sheet.
Large format and banners. A retractable banner is 33 x 80 inches. Vinyl banners come in 2x4, 3x6, 4x8 foot sizes, and step-and-repeat backdrops run 8x8 up to 10x10 feet. All of these default to 150 DPI and 0.25 bleed in the tool, because that's what a sign shop actually wants, and building them at 300 would hand you a file too big to open.
How to actually set it up
Open your design app and make a new document. Before anything else, set the document size to the trim size you want plus bleed on all four sides, and set the resolution to 300 DPI (or 150 for large format). If your app asks for a color mode, pick CMYK for commercial print, RGB only if you're printing to your own inkjet at home.
Drop guides at the trim line and at the safe margin so you can see where the cut lands and where your text needs to stay inside. Run your background art all the way out to the bleed edge. Keep your headline, logo, and any small text pulled in to the safe margin. When you export, send a print-ready PDF with crop marks and the bleed included, and tell the printer the bleed amount so their cutter knows what to do.
That's the whole workflow. The tool up top just hands you the exact pixel numbers for the document-size step so you're not doing inches-times-DPI math at midnight before a deadline.
The screen side lives next door
This page is the paper half of a pair. If you're sizing images for screens, profile photos, post graphics, link previews, the social numbers and the same kind of copy-paste tool live in the social media image size guide. That one handles crops and safe zones the way this one handles DPI and bleed, and there are per-platform versions too if you're deep in one app, like the YouTube image sizes guide for thumbnails and channel art. If you want the print tool on its own page without the article wrapped around it, it's also live at /lab/print-dimensions. Same data, same math, just the calculator.
FAQ
What DPI should I use for printing?
Use 300 DPI for anything held and viewed up close: photos, business cards, flyers, brochures, books, and letter-sized documents. Drop to 150 DPI for large-format work like posters and banners that people view from a few feet away, since the extra resolution isn't visible at that distance and only bloats your file size.
How do I convert inches to pixels for print?
Multiply the inches by your DPI. A 4x6 photo at 300 DPI is 1200 x 1800 pixels (4 x 300 by 6 x 300). For millimeter sizes like A4, convert to inches first by dividing by 25.4, then multiply by DPI. The tool above does this for all 79 sizes so you don't have to.
What is bleed and how much do I need?
Bleed is extra background art that extends past the trim line so a slightly off cut still lands inside your design instead of leaving a white edge. The US standard is 0.125 inch on every side for most print, and 0.25 inch for large-format banners where the cutting tolerance is looser.
What size is a standard US business card?
3.5 x 2 inches, which is 1050 x 600 pixels at 300 DPI. With the standard 0.125 inch bleed on all sides it becomes 1125 x 675. European cards are 85 x 55 mm and Japanese cards are 91 x 55 mm, both slightly different proportions.
What's the difference between US Letter and A4?
US Letter is 8.5 x 11 inches (2550 x 3300 at 300 DPI), the North American standard. A4 is 210 x 297 mm (roughly 2480 x 3508 at 300 DPI), the international standard used almost everywhere else. A4 is a little narrower and a little taller, so a layout built for one won't drop cleanly into the other.
Should print files be RGB or CMYK?
Commercial printers want CMYK, since paper makes color with ink rather than light. Switch your color mode to CMYK before exporting your print PDF so your bright screen colors don't shift at the press. The pixel dimensions stay the same in either mode; color mode is a separate setting from size.
Pick your size and DPI in the tool up top, add the bleed your printer asks for, and copy the pixel dimensions straight into a new document. That's the only number you actually need to get right before you start.