Is 300 DPI always required?

No. It is a convention for work that will be inspected from roughly thirty centimetres away, not a physical threshold. A banner read from four metres holds together at a fraction of it. Treat 300 as the most expensive row on the menu: worth paying for close work, wasteful for anything seen from across a room.

How many pixels is an A4 page at 300 DPI?

2,480 × 3,508 px. A4 measures 21 × 29.7 cm, which is 8.27 × 11.69 inches, and each inch costs 300 pixels along its own edge. US Letter, at 8.5 × 11 inches, costs 2,550 × 3,300 px.

Photoshop says my file is 300 DPI, so why did the print look soft?

Because the field was read at a size the pixels never covered. A 900 px logo tagged 300 DPI describes a 7.6 cm print; stretched across a 30 cm bag it arrives at 76 DPI and looks exactly like 76 DPI. Enter the pixel dimensions and the width actually ordered and the number will match what you saw.

What size gives exactly 300 DPI for my file?

Divide each pixel dimension by 300 for inches. A 2,400 × 3,000 px file lands at 8 × 10 inches, or 20.3 × 25.4 cm. Every size below that clears 300 and every size above it falls under, in direct proportion.

Do I have to upload my image to check it?

No. The checker takes two pairs of numbers — your pixel dimensions and your intended size — and divides them in the browser. Read the dimensions from Get Info on macOS or Properties → Details on Windows; the file itself stays where it is.

300 DPI checker: the pixel budget behind the number

Three hundred dots per inch is not something a file has; it is something a file achieves at a size. Ask it of a postage stamp and almost any photo clears it. Ask it of a wall poster and most do not. This page turns that into arithmetic you can run before anything is printed: how many pixels a chosen size costs, how far your pixels reach, and why typing 300 into an export dialog moves neither figure.

Your image, in pixels

Width (px)

Height (px)

The size you want to print

Print width

Print height

Keep the image's own proportions

With this on, the height follows your image so the result is not distorted.

Enter your pixel dimensions to see the resolution you would actually get.

One inch of print at 300 DPI	300 px along that edge. One centimetre costs 118 px.
A4 sheet — 21 × 29.7 cm	2,480 × 3,508 px to hold 300 DPI
US Letter — 8.5 × 11 in	2,550 × 3,300 px to hold 300 DPI
A3 poster — 29.7 × 42 cm	3,508 × 4,961 px to hold 300 DPI
Chest transfer — 28 cm / 11 in wide	3,307 px across the width alone
12 MP phone photo — 4,032 × 3,024 px	reaches 34.1 × 25.6 cm before 300 DPI is missed
Rewriting the resolution field to 300	0 px added; the budget is exactly what it was
Where SafeWidth's engine changes its decision	200 DPI, then 150 — neither of them 300

The two questions hiding inside "is this 300 DPI"

One of them is about a field stored in the file and the other is about a print. The field reads in a second and reports what some earlier piece of software intended; it carries no information about how much detail was captured. The print question — will this hold three hundred dots in every inch at the width I ordered — has a real answer, but only once a width exists. Until a size is named there is nothing for the pixels to be measured against, which is why the sentence "my image is 300 DPI" can be neither confirmed nor denied as it stands.

The pixel budget: what a size costs

At 300 DPI a size has a price in pixels, and the price is a multiplication rather than a judgement call. Every inch of finished print costs 300 pixels along that edge; every centimetre costs 118. Multiply the finished dimensions by that rate and you have the file the size requires. Anything above it is headroom, anything below it is the shortfall you will be looking at once the job comes off the press.

Pixels needed = print width in inches × 300
Working in centimetres: print width ÷ 2.54 × 300, or simply × 118
A 20 × 25 cm print costs 2,362 × 2,953 px; a 28 cm chest transfer costs 3,307 px across
The two edges are priced separately, and the edge you fall short on is the one that shows

Setting the DPI field to 300 adds no pixels

Open the image size dialog, switch resampling off, type 300 into the resolution box and save. Then look at what moved: the pixel dimensions are identical, the file occupies the same space on disk, and the checker above returns the answer it returned before. What changed is a unit label attached to a fixed quantity — the equivalent of writing "one litre" on a bottle holding five hundred millilitres. Leave resampling switched on and the pixel count genuinely rises, but the new pixels are interpolated from the ones already present, so the arithmetic returns a bigger answer while the detail stays exactly where it was.

Resampling off: the label moves, the image does not
Resampling on: pixels arrive by estimation, and estimated pixels hold no new detail
A file re-tagged to 300 and one left at 72 print identically at the same ordered width

Working it the other direction

The same rate answers the reverse question with no new formula. Divide the pixel count on an edge by 300 and you have that edge's length in inches at full detail; multiply by 2.54 for centimetres. A 3,000 px edge reaches 10 inches, or 25.4 cm. The long side of a 4,032 px phone photo reaches 13.4 inches, or 34.1 cm. That figure is not a limit the printer enforces — it is the point past which you begin spending detail instead of headroom, and the checker shows how much you are spending.

When the budget comes up short

A shortfall has three honest responses and one dishonest one. Printing smaller until the numbers meet is the cheapest, and it is frequently invisible to whoever ordered the job. Going back for the original file works more often than people expect, because what arrives attached to a message is usually a compressed copy rather than the artwork itself. Rebuilding as vector removes the budget altogether, since a vector has no pixel count to exhaust. The dishonest response is enlarging the file and then reporting the new number as though it had been measured.

Smaller print: the gap closes with no processing and nothing real is lost
Original source: ask for the export the design came from, not the copy that reached you
Vector rebuild: type and flat-colour marks redraw cleanly and stop having a maximum size
Upscaling: defensible on photographic texture, risky on lettering, and never a measurement

FAQ

Is 300 DPI always required?: No. It is a convention for work that will be inspected from roughly thirty centimetres away, not a physical threshold. A banner read from four metres holds together at a fraction of it. Treat 300 as the most expensive row on the menu: worth paying for close work, wasteful for anything seen from across a room.
How many pixels is an A4 page at 300 DPI?: 2,480 × 3,508 px. A4 measures 21 × 29.7 cm, which is 8.27 × 11.69 inches, and each inch costs 300 pixels along its own edge. US Letter, at 8.5 × 11 inches, costs 2,550 × 3,300 px.
Photoshop says my file is 300 DPI, so why did the print look soft?: Because the field was read at a size the pixels never covered. A 900 px logo tagged 300 DPI describes a 7.6 cm print; stretched across a 30 cm bag it arrives at 76 DPI and looks exactly like 76 DPI. Enter the pixel dimensions and the width actually ordered and the number will match what you saw.
What size gives exactly 300 DPI for my file?: Divide each pixel dimension by 300 for inches. A 2,400 × 3,000 px file lands at 8 × 10 inches, or 20.3 × 25.4 cm. Every size below that clears 300 and every size above it falls under, in direct proportion.
Do I have to upload my image to check it?: No. The checker takes two pairs of numbers — your pixel dimensions and your intended size — and divides them in the browser. Read the dimensions from Get Info on macOS or Properties → Details on Windows; the file itself stays where it is.

All guides