Add, subtract, multiply and divide tape-measure fractions like 3 5/8 + 1 3/16. Get the answer to the nearest 1/2 to 1/64 inch, plus decimal inches, mm and cm.
To add inch fractions, convert both lengths to a common denominator and add the numerators: 3 5/8 + 1 3/16 is 29/8 + 19/16, which is 58/16 + 19/16 = 77/16, or 4 13/16 inches. This calculator does that exactly, with no decimals along the way, then rounds the result to the finest mark you choose, from 1/2 down to 1/64 inch. You can type lengths as 3 5/8, 3-5/8, 5/8, a decimal such as 1.25, or feet and inches such as 5' 3 1/2" or 5ft 3in. A minus sign in front applies to the whole length.
Multiplying and dividing take a length and a plain number. 3 1/4 × 3 is 9 3/4 inches, and 96 ÷ 5 is 19.2 inches, which on a 1/16 tape rounds to 19 3/16 with an error of 0.0125 inch (0.32 mm). That is the cut-list case: cutting a 96 inch board into 5 equal pieces. The rounding error is shown every time, so you can see whether the nearest mark is close enough or whether to use a finer one. Ties round away from zero, so exactly half way between two marks goes to the longer one.
Switch to the second mode to turn a decimal into the nearest fraction: 0.4375 inch is exactly 7/16, while 0.3 inch is 19/64 to the nearest 1/64, short by 0.0031 inch. You can also enter millimetres or centimetres. The conversion uses 1 inch = 25.4 mm exactly, the value fixed by the 1959 international yard and pound agreement and listed by NIST. So 25.4 mm is 1 inch and 10 mm is 0.3937 inch, which is 3/8 on a 1/16 tape. A table lists the nearest mark and its error at every precision from 1/2 to 1/64.
Most US and Canadian tape measures mark 1/16 inch, and finer rules mark 1/32 or 1/64. Pick the finest mark you can actually read. A 1/16 mark is 1.5875 mm, a 1/32 mark is 0.79 mm and a 1/64 mark is 0.40 mm. Answers of 12 inches or more also show as feet and inches, so 75 1/2 inches reads as 6' 3 1/2". Inputs accept up to 12 digits before the point and 9 after it, and anything that is not a length gives a message under the box instead of a wrong answer. Everything runs in your browser and nothing you type is stored or sent anywhere. For general fractions with no units, use the fraction calculator.
Write both over 16: 3 5/8 is 58/16 and 1 3/16 is 19/16. Add them to get 77/16, which is 4 13/16 inches, 4.8125 inches or 122.24 mm.
Multiply by the precision you want and round: 0.375 × 16 = 6, so 6/16, which reduces to 3/8. On a 1/64 tape it is also 3/8 because 0.375 × 64 = 24 and 24/64 = 3/8.
1/16 inch is 1.5875 mm, because 1 inch is exactly 25.4 mm and 25.4 ÷ 16 = 1.5875. A 1/32 mark is 0.79375 mm and 1/64 is 0.396875 mm.
Divide the length by the number of pieces. 96 inches ÷ 5 = 19.2 inches, which is 19 3/16 on a 1/16 tape, 0.0125 inch short. This tool does not model saw kerf, which varies by blade (about 0.095 to 0.126 inch for common blades). For a cut list, subtract the kerf first: (96 − 4 × measured kerf) ÷ 5, since five pieces need four cuts.
Yes: 5' 3 1/2" or 5ft 3in both mean 63.5 inches. Results of a foot or more also show as feet and inches, so 63.5 inches displays as 5' 3 1/2".
It is the nearest mark minus the exact value. For 0.3 inch rounded to 1/16 the nearest mark is 5/16 = 0.3125, so the error is +0.0125 inch (+0.32 mm); a plus sign means the fraction is longer than the exact length.