Fraction Calculator: Feet Inch

The fraction calculator built for the jobsite. Add, subtract, multiply and divide feet, inches and fractions on a big, glove-friendly keypad — then switch to imperial or metric with one tap. Every answer is exact, right down to the sixteenth. Works completely offline. No account.

Stop doing tape-measure math in your head. Joist keeps a running "tape" of everything you calculate, so this morning's number is still there this afternoon.

FEET-INCH-FRACTION KEYPAD
• Enter feet, inches and fractions with fat, easy-to-hit buttons
• Add, subtract, multiply and divide measurements
• One-tap imperial to metric (mm) conversion
• Exact fraction math — no rounding drift, snaps to 1/16" or 1/32"
• A running history tape you can scroll back through

JOBSITE SOLVERS
• Stairs — risers, riser height, treads, total run, stringer length and slope angle, with code-limit warnings
• Board feet — total board footage for any lumber order
• Rafters — rafter length, run, rise, pitch and cut angle (Pro)
• Concrete — slab and tube/column yardage with waste allowance (Pro)
• Drywall — sheets needed for a room (Pro)
• Flooring — boxes needed for any floor (Pro)

Every solver ships with a clear, labeled diagram so you can see exactly what each number means.

BUILT FOR CARPENTERS, FRAMERS & BUILDERS
Whether you're framing a wall, laying out a staircase, ordering lumber, pouring concrete, hanging drywall or estimating flooring — Joist does the fraction and material math so you don't have to. A modern tool for the trades: fast, readable in the sun, and honest about its numbers.

HONEST BY DESIGN
Results are estimates to help you plan and order material. Always verify against your local building code — this app is not a substitute for it.

PRIVATE & OFFLINE
• Works with no signal, anywhere on site
• No account, no sign-up, nothing uploaded
• Your tape stays on your phone

JOIST PRO (optional)
The free app includes the calculator plus the stairs and board-feet solvers, with ads. A one-time Pro purchase unlocks the rafter, concrete, drywall and flooring solvers, removes all ads, and adds extra hi-vis themes. Pay once — no subscription.