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About this tool
Read any tape measure mark as decimal inches, millimetres and feet-inches, or snap a metric size to the nearest tape fraction.
This reader converts a tape measure mark written as a fraction — 5 3/8, 3/16, 6' 2 1/2" — into decimal inches, millimetres, centimetres and metres, and converts back the other way by snapping a metric size onto the nearest mark your tape actually carries. It uses the exact 1959 international definition of the inch, 25.4 mm, and the power-of-two divisions a tape is printed with: halves, quarters, eighths, sixteenths, thirty-seconds and sixty-fourths. It also shows how far each snapped mark sits from the true size, so you know whether the rounding matters for the joint you are cutting.
Open Tape Measure Fraction Reader on AltFTool — it loads instantly in your browser.
Paste or upload your source content.
Choose the target format or conversion mode.
Copy or download the converted result.
Accepts mixed numbers, bare fractions, foot marks and inch marks without reformatting.
Tells you in millimetres how far the nearest 1/16 or 1/32 mark is from the true size.
Every mark from 1/16 to 1 inch with its decimal and metric value, for quick reference on site.
3/8 inch is 9.525 mm exactly. The inch is defined as exactly 25.4 mm, so 0.375 x 25.4 = 9.525 — there is no rounding involved in the conversion itself.
On a standard tape the inch is halved repeatedly: the longest mark is 1/2, then 1/4, 1/8 and the shortest 1/16. Some tapes add 1/32 marks over the first inch or two. Counting the marks between the numbered inches tells you the denominator — 16 gaps means each small line is a sixteenth.
Divide the top number by the bottom number and add the whole inches. So 5 3/8 is 3 divided by 8, which is 0.375, plus 5 — giving 5.375 inches, or 136.525 mm.
100 mm is 3.937 inches, which is just under 3 15/16 in. Marking 3 15/16 leaves you 0.0125 mm long — irrelevant for carpentry, but worth knowing if you are working to machining tolerances where a 1/64 tape or a caliper is the right tool.
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