How to Use the Feet-Inches Calculator
This calculator handles arithmetic on imperial length measurements — feet, inches, and fractional inches — without requiring decimal conversion. All four arithmetic operations are supported. Results are displayed in feet-and-inches by default and can be switched to decimal inches using the unit toggle.
Entering a Measurement
Measurements are entered using the on-screen keys or a physical keyboard. The calculator accepts several formats:
- Feet and inches: type the foot value, press feet ('), type the inch value, then press inches ("). Example:
6'3"enters 6′-3″. - Fractional inches: after entering the whole-inch value, press space to begin a fraction, then type the numerator, press fraction (/), and type the denominator. Example:
6'3<space>1/2"enters 6′-3½″. - Inches only: type a value and press inches (") without entering a foot value. Example:
9"enters 9″. - Fractions only: type a fraction directly using fraction (/). Example:
3/4"enters ¾″.
A space character separates the whole-inch value from the fraction and can be entered using the space key or the SPACE button.
Arithmetic
Enter the first measurement, press an operator (+, −, ×, or ÷), enter the second value, then press =.
Operand rules:
- Addition and subtraction require both operands to be lengths.
- Multiplication requires one length and one dimensionless number. Enter the scalar as a plain number without any foot or inch suffix. Example:
5'6"×3=returns 16′-6″. - Division accepts a length divided by a dimensionless number, returning a length. Dividing a number by a length returns a dimensionless result. The keyboard entry for division is : (colon).
Chained operations are supported — pressing an operator after a completed calculation uses the previous result as the left-hand operand.
Pressing = repeatedly applies the last operator and right-hand operand again, which is useful for repetitive additions such as equal stud spacing.
Rounding
The Round selector sets the fractional precision of all displayed results. Options are 1/8″, 1/16″, 1/32″, and 1/64″. The default is 1/16″. Rounding is applied to display only — internal calculations remain at full floating-point precision. Changing the rounding setting immediately updates all values on screen, including the history.
Unit Display
The ft-in toggle in the upper right cycles the result display between two modes:
- ft-in — feet and inches with fractional inches (e.g., 14′-3 1/2″)
- in — total inches with fractional inches (e.g., 171 1/2 in)
The history panel reflects the active unit mode.
History
Completed calculations are listed in the history panel in chronological order, newest at the bottom. Up to 60 entries are retained per session. History is held in local memory only and clears when the page is refreshed - we do not record calculations. Pressing Clear Hist removes all entries immediately.
Clearing and Correcting
⌫ deletes the last character of the current entry.
CE clears the current entry without affecting the pending operator or accumulated value.
C clears everything and resets the calculator to its initial state.
Keyboard Shortcuts
| Key | Action |
|---|---|
0–9, . | Digit entry |
' | Feet separator |
" | Inches separator |
/ | Fraction separator |
Space | Space within entry |
+ | Add |
- | Subtract |
* | Multiply |
: | Divide |
Enter or = | Evaluate |
Backspace | Delete last character |
Esc | Clear all |
