Woodworking Calculators & Design Tools
Free design tools that show their work. Each calculator cites the code provision or engineering reference behind every number it gives you, so you can check the math instead of trusting a black box.
A calculator you cannot audit is just a guess with a user interface. Every tool below states its assumptions, cites the standard it checks against, and shows the limits where the method stops applying. The goal is a design you can defend, not just a number.
Why this matters: Span limits, stair geometry, and fastener sizing all have published engineering rules behind them. Working from the actual provisions keeps your build inside the envelope the codes were written to protect.
Design Tools
Interactive builders and calculators, each grounded in a published standard
Deck Design
Deck Builder
Enter your deck size and get a DCA 6 compliance check, an honest parts list, and printable framing plan and elevation drawings. A permit-style packet in your browser, with joist, beam, footing, and ledger checks cited to the provision.
Stair Design
Stair Calculator
Straight, L-shaped, and winder stairs with dimensioned stringer layout and cut diagrams. Rise, run, headroom, and throat depth are checked against IRC limits so you know exactly which dimension is out of bounds and by how much.
Stair Design
Winder Stair Calculator
Balanced winder treads laid out to the IRC walkline rules, with a dimensioned cut template for every wedge.
Stair Design
L-Shaped Stair Calculator
Stairs that turn 90 degrees on a landing: riser split, landing size, and stringer cuts for both flights.
Shelf Design
Shelf Sag Calculator
Predict shelf deflection from span, load, material, and thickness before you cut a board. See how close your design sits to the visible-sag threshold and what moving a support or thickening the shelf actually buys you.
Fastener Sizing
Pilot Hole Chart & Thread Engagement Calculator
Pilot, clearance, and countersink sizes for standard wood screw gauges, straight from the NDS dimension tables, plus a thread engagement calculator that tells you how much of your screw is actually holding.
How These Tools Calculate
Cited, Not Asserted
The checks behind these tools come from published standards: DCA 6 for deck framing, the IRC for stair geometry, and the NDS for fastener dimensions. The Woodworking Standards library collects the provisions themselves in plain English.
Stated Assumptions
Every method has limits: species, grade, load model, and moisture all change the answer. The Assumptions & Methodology page documents the conservative defaults these tools use and where you must verify against your local code.
Findings, Not Verdicts
These tools tell you what the published rules say about your dimensions. They do not replace a permit, an inspector, or an engineer for anything structural you are not qualified to judge yourself.