Show the formula and working
This free photo frame size converter turns frame and print sizes between inches, centimetres and A paper sizes, then works out which standard frame to buy once you add a mount, for anyone in the UK, Ireland and Europe who shops between inch and metric frames. It also shows how much of a camera or phone photo is cropped to fit.
Quick answer: A photo frame size converter multiplies inches by 2.54 to get centimetres. A 6 x 4 in frame is 15.2 x 10.2 cm, 7 x 5 in is 17.8 x 12.7 cm and 10 x 8 in is 25.4 x 20.3 cm. Metric frames such as 13 x 18 cm are close to, but not the same as, inch sizes.
What Is a Photo Frame Size Converter?
A photo frame size converter is a tool that translates a frame or print size from one measuring system to another and finds the matching standard frame. Frame sizes describe the picture the frame holds, not the outside of the moulding, so a 10 x 8 in frame takes a 10 x 8 in print or mount.
The formula in plain words: one inch is exactly 25.4 mm, the value fixed in 1959 and confirmed by the NIST guide to SI units of length. Multiply inches by 2.54 for centimetres, or divide centimetres by 2.54 for inches. To size a frame with a mount, take the print size, subtract the small overlap the mount covers on each edge, then add the mount border twice to each side. The smallest standard frame at least that big is the one to buy.
How Do You Use the Photo Frame Size Converter?
- Choose a Direction: “Standard size to cm and inches”, “Custom size in cm” or “Custom size in inches”.
- For a standard size, pick it from Standard print or frame size. For anything else, type Width (custom) and Height (custom) in the unit you chose.
- Enter the Mount border width you want on each side, or 0 for no mount.
- Keep Mount overlap on each edge at about 0.5 cm, or use the figure your framer gives you.
- Pick the Photo shape from the camera to see how much of the image will be cropped.
- Read the result and open “Show the formula and working” to see the mount window, the frame size needed and every step.
What Size Is a 6 x 4 Photo Frame in cm?
A 6 x 4 in photo frame holds a print of 15.24 x 10.16 cm, usually rounded to 15 x 10 cm. In much of Europe the same print is sold as 10 x 15 cm, which is 2 mm narrower and 2 mm shorter, so a 10 x 15 cm print fits a 6 x 4 in frame with a little room to spare. The 6 x 4 in print has a 3:2 shape, the same as most DSLR and mirrorless cameras, so it prints without cropping.
Is 13 x 18 cm the Same as 7 x 5 Inches?
No: 13 x 18 cm is about 3 mm wider and 2 mm longer than 7 x 5 in, which is 12.7 x 17.8 cm. The difference is small, but a 13 x 18 cm print can buckle or need trimming in a tight 7 x 5 in frame. A 7 x 5 in print in a 13 x 18 cm frame may slip at the edges unless a mount or backing holds it. The tool shows the nearest size in the other system and the gap in millimetres.
What Size Frame Do You Need for a Photo With a Mount?
As a rule of thumb, a mount moves you up one or two standard frame sizes: a 7 x 5 in photo with a 4 cm mount needs a 10 x 8 in frame. The mount window is cut slightly smaller than the print so the photo does not fall through, which is why the tool subtracts the overlap first. Wide mounts suit small photos on large walls. If you are repainting before hanging a gallery wall, the paint calculator works out how much emulsion the wall needs.
Will My Phone Photo Fit a Standard Frame Without Cropping?
A photo only fits without cropping when its shape matches the frame: 3:2 camera images suit 6 x 4 in and 12 x 8 in, while 4:3 phone images suit 8 x 6 in. Put a 3:2 photo in a 10 x 8 in frame and about 17% of the width is lost. A 7 x 5 in print loses about 7% of a 3:2 image and about 5% of the height of a 4:3 image. A4 and the other ISO 216 paper sizes share a 1.414 shape, close to 3:2 but not identical.
Photo Frame Sizes: UK, EU and US Comparison
| UK and US (inches) | Exact size in cm | Nearest EU metric size | Shape |
|---|---|---|---|
| 6 x 4 in | 15.2 x 10.2 | 10 x 15 cm | 3:2 |
| 7 x 5 in | 17.8 x 12.7 | 13 x 18 cm | 7:5 |
| 8 x 6 in | 20.3 x 15.2 | 15 x 20 cm | 4:3 |
| 10 x 8 in | 25.4 x 20.3 | 20 x 25 cm | 5:4 |
| 12 x 8 in | 30.5 x 20.3 | 20 x 30 cm | 3:2 |
| 12 x 10 in | 30.5 x 25.4 | 24 x 30 cm | 6:5 |
| 16 x 12 in | 40.6 x 30.5 | 30 x 40 cm | 4:3 |
| 20 x 16 in | 50.8 x 40.6 | 40 x 50 cm | 5:4 |
| 11.69 x 8.27 in | 29.7 x 21.0 | A4 | 1.414 |
| 16.54 x 11.69 in | 42.0 x 29.7 | A3 | 1.414 |
The inch sizes and their European equivalents follow the common photo print sizes used by photo labs. In the UK, shops usually write the long side first (7 x 5 in), while US shops write the short side first (5 x 7 in). Both describe the same frame.
Worked Example: Framing a 7 x 5 Print With a Mount
Example: a 7 x 5 in holiday print taken on a mirrorless camera needs a 4 cm mount around it. Choose “Standard size to cm and inches”, pick 7 x 5 in, set the mount border width to 4 cm, keep the overlap at 0.5 cm and select 3:2 as the camera shape.
- Print size: 7 x 2.54 = 17.8 cm by 5 x 2.54 = 12.7 cm.
- Mount window: 17.8 minus 1 = 16.8 cm by 12.7 minus 1 = 11.7 cm.
- Frame size needed: 16.8 + 8 = 24.8 cm by 11.7 + 8 = 19.7 cm.
- Smallest standard frame that fits: 10 x 8 in or 20 x 25 cm.
- Crop: the print is 1.4 long to short, the camera image 1.5, so about 7% of the width is trimmed when printing.
For more tools for measuring and sizing around the house, see the home calculators.
Photo Frame Size Converter FAQs
Is a frame size the inside or outside measurement?
A frame size is the inside measurement: the size of print, mount or glass the frame holds. The outside size depends on the moulding width, so a 10 x 8 in frame with a 2 cm moulding measures about 4 cm more each way on the wall.
What size is an A4 frame in inches?
An A4 frame holds 21.0 x 29.7 cm, which is 8.27 x 11.69 in. It is close to 12 x 8 in, but a 12 x 8 in frame is about 7 mm too narrow, so an A4 certificate needs an A4 frame or a 12 x 10 in frame.
What frame do I need for an 8 x 10 photo with a mount?
An 8 x 10 in photo with a 4 cm mount and 0.5 cm overlap needs a frame of about 32.4 x 27.3 cm. The smallest standard frames that fit are 14 x 11 in or 30 x 40 cm. With a slimmer 2.5 cm border, a 12 x 10 in frame is enough.
Will a 10 x 15 cm photo fit a 6 x 4 frame?
Yes. A 10 x 15 cm print is about 2 mm smaller each way than a 6 x 4 in frame, which holds 10.2 x 15.2 cm. The backing board and glass keep it in place, and a mount hides the small gap completely.
How much overlap should a mount have?
A mount window is normally cut a few millimetres smaller than the print on every edge so the photo cannot slip through. This tool uses 0.5 cm as an editable example. Ask your framer for their figure, as some use less for prints with important detail near the edge.
How do I convert a frame size from cm to inches?
Divide each side in centimetres by 2.54. A 30 x 40 cm frame is 11.81 x 15.75 in, so it is slightly smaller than a 16 x 12 in frame, which is 30.5 x 40.6 cm. Never assume a metric frame equals the nearest inch size.
Checked October 2026. Sources: NIST, SI units of length, Wikipedia, Paper size (ISO 216), Wikipedia, Photo print sizes.