Feet and Inches Length Calculator
Add, subtract, multiply, and divide feet, inches, and fractions. Get results in feet-inches, decimal feet, yards, meters, cm, and mm.
📏 Feet and Inches Calculator
IMPERIAL
METRIC
💡 Construction Math: Feet and Inches
Feet and inches math is essential for US construction, carpentry, and home improvement. This calculator handles addition, subtraction, multiplication, and division of measurements with fractional inches — the same fractions found on a tape measure.
Need to convert fractions? Use our inch fraction calculator. For area calculations, see our square footage calculator or square yards calculator.
How to Add Feet and Inches
- Convert fractional inches to decimals: 3/8" = 0.375", 1/2" = 0.5", etc.
- Add feet separately, add inches separately
- Carry over: if inches ≥ 12, subtract 12 and add 1 to feet
Example: 10' 6 3/8" + 5' 3 1/4" = 15' 9 5/8"
- Feet: 10 + 5 = 15
- Inches: 6.375 + 3.25 = 9.625 = 9 5/8"
- Result: 15' 9 5/8"
Common Fraction Addition Reference
| A | + B | = Result |
|---|---|---|
| 1/8" | 1/8" | 1/4" |
| 1/4" | 1/4" | 1/2" |
| 3/8" | 1/4" | 5/8" |
| 1/2" | 1/4" | 3/4" |
| 1/2" | 1/2" | 1" |
| 5/8" | 3/8" | 1" |
| 3/4" | 1/2" | 1 1/4" |
| 7/8" | 5/8" | 1 1/2" |
How to Multiply and Divide
Multiply: Convert to decimal inches, multiply by the factor, convert back.
Example: 5' 6" × 3 = 66" × 3 = 198" = 16' 6"
Divide: Convert to decimal inches, divide by the factor, convert back.
Example: 10' 0" ÷ 4 = 120" ÷ 4 = 30" = 2' 6"
Feet and Inches to Metric
| Feet & Inches | Decimal Feet | Meters | Centimeters |
|---|---|---|---|
| 1' 0" | 1.0 | 0.3048 | 30.48 |
| 3' 0" | 3.0 | 0.9144 | 91.44 |
| 5' 0" | 5.0 | 1.524 | 152.4 |
| 5' 6" | 5.5 | 1.676 | 167.6 |
| 6' 0" | 6.0 | 1.829 | 182.9 |
| 8' 0" | 8.0 | 2.438 | 243.8 |
| 10' 0" | 10.0 | 3.048 | 304.8 |
Common Length References
| Item | Typical Length |
|---|---|
| Standard door height | 6' 8" (80") |
| Standard door width | 2' 8" or 3' 0" |
| Ceiling height | 8' 0" or 9' 0" |
| Wall stud | 92 5/8" (pre-cut for 8' walls) |
| Sheet of plywood | 4' × 8' (48" × 96") |
| Standard 2×4 lumber | 8', 10', 12', 16' lengths |
| Countertop height | 3' 0" (36") |
| Stair riser | 7" to 7 3/4" |
For area calculations with these measurements, try our square footage calculator or square meters calculator.