DPI Calculator for Printing

A 4032 × 3024 px photo prints at 13.44 × 10.08 in at 300 dpi: turning pixels into print size

DPI says how many pixels are laid down in one inch of a print. That gives one formula that ties everything together: pixels ÷ DPI = inches. A 12 MP phone photo (4032 × 3024 px) printed at 300 dpi measures 4032 ÷ 300 = 13.44 in, or 34.14 cm, so it easily covers a Letter page (11 × 8.5 in in landscape).

Enter any two of the three values and this calculator finds the third. You can see how large a photo can be printed, how many pixels a Letter page or a 4×6 print needs at 300 dpi, and what dpi you get when you put the photo you already have onto a given sheet. The DPI here is print resolution, which is a different thing from the DPI (or CPI) setting for mouse sensitivity.

When to check DPI before printing

• Before sending a file to a print shop or photo lab: the question is always how many pixels the file has at the size you will print it. The Epson guidance cited below recommends 300 to 360 dpi for output at the final print size.
• Ordering photo prints or choosing a frame: you can tell in advance whether a photo holds up at 8×10 in or 11×17 in. The per-paper dpi cells give the answer at a glance.
• Making posters and large prints: at 300 dpi a poster file easily reaches hundreds of megabytes. Matching the resolution to the viewing distance keeps the difference invisible from that distance and makes the file far lighter.
• Starting a new design canvas: in Photoshop and similar programs, you set the new document's width and height in pixels from the paper size and resolution.

How to use the calculator

1. Choose what to solve for: at the top, pick print size, pixels needed or DPI. The chosen field becomes the result and carries a "Result" tag.
2. Enter the other two values: type numbers directly, or use the lists under each field for phone and camera megapixels, common resolutions, and Letter, 4×6 or 8×10 paper. If you pick from the list of the field being solved, the calculator switches modes for you.
3. Open a photo: the calculator reads its width and height in pixels and draws the photo to scale on the mat. The file stays inside this browser and is not sent anywhere.
4. Place it on paper: when solving for DPI, the paper is rotated to match the photo, then calculated either as Fit (whole photo inside, with margins) or Fill (paper fully covered, with cropping).
5. Read the result: the mat shows the paper outline and print size, and the cells below show the dpi on each paper. The 5 mm magnifier and distance ruler show how fine that resolution really is. "Copy link" copies an address that holds the current values.

How the calculation works

One inch is defined as 25.4 mm, so if you enter a length in millimetres it is divided by 25.4 before calculating.

• Print size = pixels ÷ DPI × 25.4 mm. Example: 4032 ÷ 300 × 25.4 = 341.4 mm (13.44 in).
• Pixels needed = length in inches × DPI, rounded. Example: the 11 in side of Letter at 300 dpi needs 11 × 300 = 3,300 px, and the 8.5 in side needs 2,550 px. For A4, 297 ÷ 25.4 × 300 = 3,507.9, which rounds to 3,508 px.
• DPI = pixels ÷ length in inches. Horizontally and vertically give two values; Fit uses the larger one and Fill the smaller one. With the larger value the whole photo fits inside the sheet, and with the smaller one the sheet is completely covered.
• Distance where pixels vanish = the distance at which one pixel (25.4 ÷ DPI mm) spans 1 arcminute, that is (25.4 ÷ DPI) ÷ tan(1 arcminute). At 300 dpi it is 291 mm (about 11.5 in).
• Uncompressed size = pixels × 3 bytes (8-bit RGB) or × 4 bytes (CMYK), divided by 1,048,576. A saved JPG or PNG is much smaller because of compression.

Pixels needed for common paper sizes

Paper sizes converted to pixels at two resolutions. If your photo is at least this large, it can fill that resolution.

Letter, Legal and Tabloid are the usual U.S. sheet sizes, and A4 and A3 follow ISO 216. Letter is slightly wider and shorter than A4 (8.5 × 11 in against 8.27 × 11.69 in), so a file built for one needs adjusting for the other. A 4×6 in print needs only 1,200 × 1,800 px (2.2 MP) at 300 dpi, which almost any phone photo provides.

What common photos can print

The size at 300 dpi, and the resolution you get when the photo is fitted onto Letter, Tabloid and an 18×24 in poster. The paper orientation is matched to the photo.

A 12 MP phone photo stays above 200 dpi even on Tabloid (274.9 dpi). By contrast, a 1080 px image saved from social media comes out at only 127.1 dpi on Letter, which is too little for something held close.

How many dpi is enough: it depends on viewing distance

A person with normal sight, measured as 20/20 on the Snellen chart, can tell apart two objects that subtend a visual angle of 1 arcminute (1/60 of a degree). If a printed pixel looks smaller than that, the edges between pixels disappear, so the farther away you look, the lower the resolution you need.

This is why 300 dpi is the usual reference for prints held in the hand. Epson recommends 300 to 360 dpi, notes that the suitable level depends on viewing conditions, and says that 200 dpi or more gives a satisfactory print, with 300 or more giving a high-resolution one. For large prints the table does the work: from 3 ft away, 100 dpi is already above the 95.5 dpi in the 3 ft row. A 24×36 in poster at 300 dpi would be 7,200 × 10,800 px, around 222.5 MB uncompressed, while at 100 dpi it is 2,400 × 3,600 px.

The 72 dpi stored in a file says nothing about quality

Open a photo's properties and you may see 72 dpi, or 96 dpi. That number is only a note about how many pixels per inch the picture is meant to be printed at, and the Exif standard says to write 72 when the resolution is unknown. The same photo can therefore be tagged 72 by one device or program and 300 by another.

What decides print quality is the pixel count and the size you print at. A 4032 × 3024 px photo fitted onto Letter prints at 366.5 dpi whether the file says 72 or 300. In Photoshop, if Resample is turned off and you change only the resolution, the pixels stay the same and only the document's stated print size changes.

When the photo and paper proportions differ: Fit and Fill

Letter has an 8.5:11 shape, which does not match a 4:3 or 3:2 photo, so something is left over or missing. Fit keeps the whole photo and leaves margins; Fill covers the whole sheet and crops the edges. The table below uses Letter, rotated to match the photo.

Fill always gives a lower resolution than Fit, because the photo has to be enlarged to cover the sheet. For a picture with very different proportions, such as a 16:9 screenshot, Fill crops a lot from the sides, so check the mat drawing first to see what gets cut.

Common mistakes

• Just typing 300 into the resolution box: if the pixels stay the same, only the print size shrinks. Printing Letter at 300 dpi takes at least 2,550 × 3,300 px.
• Enlarging a small image to reach 300 dpi: resampling adds pixels, so the number looks right, but no detail that was missing from the original appears. The blur just gets bigger.
• Putting a landscape photo on a portrait sheet unrotated: fitted to Letter held upright, a 4032 × 3024 px photo becomes 8.5 × 6.38 in and about 40% of the page stays blank, while Fill crops a lot from the sides. With the sheet turned sideways it fits at 11 × 8.25 in. This calculator turns the paper to match automatically.
• Insisting on 300 dpi for big prints: a 24×36 in poster at 300 dpi is 7,200 × 10,800 px and about 222.5 MB uncompressed in RGB. Use the viewing distance, and what the print provider asks for, to choose.
• Forgetting the extra for trimming: print providers often ask for a little more than the final size so the cut falls inside the artwork. Calculate the pixels you need from the working size they specify.

Limits and cautions

• The distance where pixels disappear assumes 20/20 vision, good light and clear contrast. If your eyesight is sharper, or there are fine lines and small text, pixels may be visible from closer than the table says.
• The dpi here is the number of image pixels per inch (PPI). It is not the number of ink dots listed in a printer's specifications, such as 1200 or 2400 dpi.
• Real print quality also depends on the original's focus, noise and compression, the paper, and the printing method. A blurry photo prints blurry even at a high resolution.
• The uncompressed size assumes 8-bit RGB or CMYK; 16-bit doubles it. Saved JPG, PNG or PDF files are far smaller because of compression.
• Pixels needed are rounded, as in a new Photoshop document, so converting back can differ from the original size by less than 0.1 mm.
• Photos the browser cannot open, such as HEIC, cannot be read for their pixel size. In that case look up the width and height in the photo's info and type them in.

Reference date 2026-10-20 · A-series sizes follow ISO 216 and the viewing standard is 20/20 vision (1 arcminute). Letter, Legal, Tabloid and the photo sizes are the usual U.S. sheet sizes in inches. The calculation uses 1 in = 25.4 mm and 1 MB = 1,048,576 bytes, which do not change from year to year. Ask your print provider for its own recommended resolution.

Sources

• 01ISO 216:2007 Writing paper and certain classes of printed matterA-series paper sizes
• 02NCBI StatPearls: Visual Acuity20/20 vision resolves objects 1 arcminute apart
• 03CIPA DC-008-2012 Exif 2.3XResolution and YResolution default to 72; 72 is used when the resolution is unknown
• 04Adobe Photoshop: Set image size and resolutionMeaning of resolution (ppi) and Resample
• 05Epson: What is the recommended resolution for output print size?300 to 360 dpi recommended; 200 dpi or more gives a satisfactory print

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