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Carpentry
Calculators
Forty free calculators for cut lists, stairs, rafters, crown molding and more — shop math that works on your phone, with nothing to install.
Getting started
- Inch fraction calculatorAdd or subtract two measurements written the way a tape shows them, read to the nearest sixteenth, thirty-second or sixty-fourth.
- Board cut calculatorHow many pieces of one length come out of a board of another, with the kerf charged between cuts and the leftover shown.
- Sheet layout calculatorHow many same-size panels fit on a sheet of plywood in a plain grid, turned 90° if that fits more.
- Pilot hole calculatorThe right drill bit for a wood screw, by gauge number and by softwood or hardwood.
- Pocket hole screw calculatorScrew length and thread by material thickness, and how far apart to space the holes along an edge joint.
- Panel glue-up calculatorHow many boards it takes to glue up a target panel width, and how much wider to glue up so the rip lands clean.
- Baseboard calculatorLinear footage of flat trim for a room from its perimeter and its doorways, with a waste allowance.
- Miter angle calculatorThe miter for baseboard, casing or chair rail at any corner angle — flat trim, so there's no bevel to set.
- Circle and arc layoutA trammel arm's length for a full circle, or the radius of a shallow arc from its chord and rise.
- Grid enlargement calculatorScale a small pattern up to full size using the classic square-by-square grid method.
Buying material
- Cut list optimizerLay your parts out on a sheet of plywood and get the cuts in order. Accounts for blade kerf and keeps the grain running the right way.
- Board foot calculatorHow much lumber to buy for a finished piece, what it will cost, and what to ask for at the yard.
- Weight calculatorWhat a board or a stack of sheet goods weighs — for shelf brackets, a car boot, or a freight quote.
- Deck and fence takeoffBoards, joists, posts, pickets, screws and bags of concrete, with the gaps between boards properly counted.
- Roofing calculatorSquares, bundles, starter strip, ridge cap and underlayment from a building footprint and a pitch.
- Wall framing stud countField studs at 16" or 24" on centre, corner studs, and the king and jack studs every opening adds.
- Fastener calculatorScrews or nails for a sheet good on an edge-and-field pattern, with the box count to buy.
- Paint and finish coverageGallons from an area and a coat count, with the cans to buy for brush, roller or spray.
- Concrete footings and slabsCubic yards for a run of post footings or a slab, and the bags of ready-mix that buys.
Cutting and joinery
- Crown molding anglesThe miter and bevel for any corner and any spring angle, plus the single setting for cutting it nested.
- Dovetail and box joint templatesSet out the joint, print it at true 1:1 scale, and glue the paper straight onto the board.
- Wood movementHow far a panel expands and shrinks with the seasons, and what that means for the joint holding it.
- Segmented rings and columnsMiter and bevel for any number of sides, flat or flared, and how long each segment has to be.
- 3-4-5 square checkThe diagonal that proves a corner square from any two leg lengths, scaled up for a full building corner.
- Mortise and tenon sizingTenon thickness and shoulder by the rule of thirds, and the length a blind or through mortise allows.
- Picture frame miter cutsCut lengths, long point to long point, for a rectangular mitered frame, and how much molding to buy.
Layout
- Stair stringersDivide the rise into even risers, lay out the notches, and check the result against the code.
- Baluster and slat spacingEven gaps across any span, checked against the 4-inch guard rule, with tape-measure marks that don't drift.
- Wainscoting layoutEven picture-frame boxes across a wall, drawn as an elevation with the cut lengths underneath.
- RaftersCommon, hip and jack rafters for any pitch, with the birdsmouth laid out and the cut angles alongside.
- Flooring and decking layoutHow many rows, how wide to rip the first one, and where the end joints fall so they never line up.
- Tile layoutFull tiles across the middle and a sized cut tile at every edge, centred or started from one wall.
- Shelf-pin hole layoutHole count and marks down a cabinet end panel, on the 32mm system or a plain 1" pitch.
- Fence post spacingPost count and the actual on-centre spacing for any run and maximum span.
Cabinets and shelves
- Drawer boxesBox sizes and a cut list from the opening, with the slide clearances rounded the way that still fits.
- Shelf sag and spanHow far a shelf bends under books, how far it can span, and what a strip on the front edge buys you.
- Cabinet boxesA carcass cut list from the finished outside dimensions, face-frame or frameless.
- Closet shelvingShelf and rod heights for a single-hang, double-hang or shelf-only closet, with the shelf's sag checked.
- Cabinet hinge count and placementHinge count from door height, and where each one sits down the door.
- Countertop overhang supportWhether an overhang needs corbels or brackets, and how many, by material and run length.
What you get
Rise per step
7 1/8"
Run per step
10 1/2"
Every calculator answers first and explains after — checked against the 2021 IRC where a code applies, with a diagram and cut marks laid out below it. This is the stair calculator's own worked example, live.
Open the stair calculator →Questions about this site
- Is this actually free?
- Yes, all forty calculators, with nothing metered or paywalled. There is no account and nothing to upgrade — the site is paid for by page-view analytics that carry no cookie and no identifier, not by a subscription.
- Do I need to sign up or install anything?
- No. Every calculator runs in your browser tab; there is no account, no app, and nothing to download. Add the site to your phone's home screen if you want an icon for it, and it opens exactly the same page, faster.
- Are the numbers checked against a building code?
- Where a code applies — stair risers and treads, guard baluster spacing, rafter birdsmouths — the calculator checks the result against the 2021 IRC and says so on the page. Those figures are defaults, not law: codes are amended locally, so the page also says to ring the building department before you cut, not after.
- Do you store my measurements?
- Nothing you type is sent anywhere — there is no server to send it to. Two things are kept in your browser's local storage, on your device: the cuts you've ticked off in the cut list optimizer, and, when you send a cut list from one calculator to another, the parts themselves so the second page can pick them up. Both are readable only by this site and cleared whenever you clear your browser data.
- Why do the calculators start with numbers already filled in?
- Each one opens on a real job — a four-drawer cabinet, a 57" deck stair, 38° crown in a square corner — so you see a finished answer before you change anything. Edit any field and the answer below it updates as you type.