Shim: Construction Calculator

Shim is a construction calculator for contractors, carpenters, framers and DIY builders. Add feet, inches and fractions exactly, then work out concrete, drywall, roofing, stairs, rafters, tile and paint in seconds. Every trade calculator is free, works offline, and shows its work.

FEET INCH FRACTION CALCULATOR
• Type 5' 7-3/8" + 2' 6-7/8" and get 8' 2-1/4", exactly
• Add, subtract, multiply and divide feet, inches and fractions
• Fraction precision from 1/2" to 1/64"
• Switch to decimal feet, decimal inches, mm, cm or meters
• Length × length gives square feet; × again gives cubic yards
• Memory keys and a tape of past calculations you can reuse and copy

CONSTRUCTION CALCULATORS, ALL FREE
• Concrete calculator: slabs, footings and round columns (sonotubes) in cubic yards, cubic feet or cubic meters, with 80, 60, 50 and 40 lb bag counts and a ready-mix order amount
• Drywall calculator: walls and ceiling minus doors and windows, in sheets of 4×8, 4×10, 4×12 or 54"×12'
• Paint calculator: wall and ceiling area, coats and coverage, in gallons
• Tile and flooring calculator: several rooms or areas, waste for straight or diagonal layouts, in boxes and tiles
• Roofing calculator: roof area, squares and shingle bundles, plus a roof pitch converter (rise/12, degrees and percent)
• Stair calculator: number of risers and treads, riser height, total run, stringer length and angle, with building code warnings
• Rafter calculator: common rafter length, overhang and cut angles
• Board foot calculator for lumber, with nominal or actual sizes
• Right triangle calculator and squaring diagonals for layout
• Unit converter for length, area, volume and weight

SEE IT IN 2D AND 3D
Open a simulation from any trade calculator to see your slab, room, stairs, roof or boards drawn to scale. Rotate and zoom the 3D view to check your numbers before you order materials.

SHOWS ITS WORK
Tap "Show steps" on any result to see the formula, your numbers and where each default value comes from. Exact fractions are kept until the final answer, and any rounded result is marked with ≈. Material counts always round up, so you don't come up short.

BUILT FOR THE JOB SITE
• Big, glove-friendly keys
• High-contrast Sunlight theme for bright sun
• Works offline on any construction site, with no account and no login
• Keep-screen-on option and vibration feedback
• English and Spanish

SHIM PRO: BUY ONCE, NO SUBSCRIPTION
• Save calculations into projects for each job
• PDF estimates with your company name and logo
• Material cost estimating
• Your own presets for bag sizes, sheet sizes and coverage
• Unlimited tape history
• No ads
Pro restores automatically on a new phone. Backup export and import are free for everyone.

Results are estimates. Check local building codes and manufacturer specs before you build or order.