Measurement & Materials
Feet and inches
Add or subtract two measurements, or multiply one length by a count, with fractional-inch entry and decimal conversions.
Your inputs
Complete the fields for your selected method. Zero means intentionally zero, not unknown. Currency selection labels amounts; it does not convert exchange rates.
How this calculation works
total inches = feet × 12 + inches; add, subtract or multiply as selected; decimal feet = total inches / 12
Enter feet and the remaining inches separately; inches must be below 12. Fractions such as 1/2 and mixed numbers such as 7 1/2 are supported. Multiplication scales a length, not an area. This is measurement arithmetic, not a cutting layout or tolerance specification.
What information do I need?
Use records for the same job, equipment or accounting period. Only the fields for your selected entry method are required. An unknown amount is not zero.
Input definitions and where to find them
- Calculation: Use matching records or an explicitly identified assumption for calculation. Unknown is not the same as zero.
- First measurement — whole feet (ft): Use matching records or an explicitly identified assumption for first measurement — whole feet. Unknown is not the same as zero.
- First measurement — inches (7.5 or 7 1/2): Use matching records or an explicitly identified assumption for first measurement — inches (7.5 or 7 1/2). Unknown is not the same as zero.
- Second measurement — whole feet (ft): Use matching records or an explicitly identified assumption for second measurement — whole feet. Unknown is not the same as zero. Used with: Add two lengths.
- Second measurement — inches: Use matching records or an explicitly identified assumption for second measurement — inches. Unknown is not the same as zero. Used with: Add two lengths.
- Subtract — whole feet (ft): Use matching records or an explicitly identified assumption for subtract — whole feet. Unknown is not the same as zero. Used with: First length minus second length.
- Subtract — inches: Use matching records or an explicitly identified assumption for subtract — inches. Unknown is not the same as zero. Used with: First length minus second length.
- Number of first-length equivalents (count): Use matching records or an explicitly identified assumption for number of first-length equivalents. Unknown is not the same as zero. Used with: Multiply first length by a count.
Use the Where to find this value controls beside the inputs for available work-it-out helpers. Estimates remain your assumptions; a helper does not verify the source figures.
Worked example
Example amounts use US dollars (USD).
Example answer: Decimal length is 15.979167 ft for the illustrative inputs below.
Example inputs
- Calculation: Add two lengths
- First measurement — whole feet: 12 ft
- First measurement — inches (7.5 or 7 1/2): 7 1/2
- Second measurement — whole feet: 3 ft
- Second measurement — inches: 4 1/4
- Decimal length
- 15.979167 ft
- Total inches
- 191.750000 in
- Feet and inches (nearest 1/16 inch)
- 15 ft 11 3/4 in
- Length in meters
- 4.870450 m
- Fractional display rounds to the nearest 1/16 inch. Decimal results retain calculation precision. A negative subtraction result means the second length is longer.
These illustrative values are not recommended rates or industry averages. Replace every example input with your own figures.
Use the result well
Use the net measured quantity to check a material order or quote. Keep installed area, extra material and purchased quantities separate.
Keep inputs on the same scope and time basis. Calculations retain precision internally; displayed values generally round to two decimal places, with extra precision for very small values and whole-unit rounding where required. Economic comparisons describe your supplied assumptions and do not guarantee future results.
This tool provides business arithmetic. It does not approve engineering designs, establish legal or tax treatment, select equipment or certify safe operating conditions.