Fraction Calculator
Add, subtract, multiply, and divide fractions. Results in tape-measure-friendly format.
Result
4 3/4
= 4.75
Tape Measure
Working with fractions in woodworking
Fractions are the native language of the woodshop. Tape measures read in halves, quarters, eighths, and sixteenths. Lumber dimensions like 3/4" plywood, 1-1/2" face frames, and 5/4 decking are all fractional. Joinery measurements — mortise depths, tenon shoulders, dado widths — almost always land on a fraction.
When you need to combine two measurements or split a dimension, doing fraction arithmetic by hand is error-prone, especially under shop conditions. This calculator handles the math and converts the result to the nearest mark on your tape measure, so you can go straight from screen to cut list.
How to add and subtract fractions
The key is finding a common denominator. Multiply both denominators together, convert each fraction, then combine the numerators.
Example 1: 3/4 + 1/8. Common denominator: 8. Convert: 6/8 + 1/8 = 7/8.
Example 2: 5-1/2 − 2-3/4. Convert to improper fractions: 11/2 − 11/4. Common denominator: 4. That's 22/4 − 11/4 = 11/4 = 2-3/4.
For multiplication, multiply the numerators together and the denominators together, then simplify. For division, flip the second fraction and multiply. This calculator handles all of it, including simplification to lowest terms.
Inch fractions and your tape measure
Standard tape measures divide each inch into fractions with power-of-2 denominators: 1/2, 1/4, 1/8, and 1/16. Higher-precision tapes go to 1/32. The graduation marks get shorter as the denominator increases — the 1/2" mark is tallest, 1/16" marks are the smallest.
This means fractions like 1/3, 1/5, 1/6, and 1/7 don't appear on any tape measure. If your calculation yields one of these, you need the nearest tape-measure equivalent. For example, 1/3" is closest to 5/16" on a 16th-inch tape, or 11/32" on a 32nd-inch tape. This calculator shows you both the exact result and the closest tape-measure reading at your selected precision.
Frequently asked questions
- What is 1/3 on a tape measure?
- 1/3 inch doesn't appear on a standard tape measure. The closest mark is 11/32" (on a tape with 32nd-inch markings) or 5/16" (on a 16th-inch tape). Always check which precision your tape measure supports.
- How do I add fractions with different denominators?
- Find a common denominator by multiplying the two denominators. Convert both fractions, add the numerators, then simplify. For example: 1/4 + 1/3 = 3/12 + 4/12 = 7/12.
- What fractions are on a tape measure?
- Standard tape measures show fractions with denominators that are powers of 2: 1/2, 1/4, 1/8, 1/16, and sometimes 1/32. The longer the mark, the larger the fraction.
- Can I use this for inch fractions?
- Yes. This calculator works with any fractions, including the inch fractions used in woodworking. Results show exact fractions and the nearest tape-measure equivalent.