Deck Planner: a free deck calculator that draws your deck

Type the width, depth and height of your deck. Deck Planner draws it to scale with every joist, beam, post and footing, checks joist and beam spans against published span tables, and lists what to buy. It runs in your browser, saves on this device and needs no account.

The tool is above this text. Scroll up to plan a deck. Available in English and Spanish.

What you get for free

• A plan view drawn to scale: ledger, joists at their real spacing, beams, posts, footings and stairs, with dimensions.
• Joist span and beam span checks. Each choice shows the table limit it was checked against, and a choice that is past its limit is flagged with the next one that passes.
• Footing count and size for your posts, with the concrete to buy.
• Decking board count, fasteners, railing posts and balusters, and stair rise, run and stringers.
• A material list for the whole deck: framing lumber, joist hangers, post bases, concrete, decking and screws, grouped the way you shop for it.
• One saved project, kept on this device.

What the iPhone app adds

One purchase of $9.99 in the app unlocks PDF export of the plan, material list and cut list; a cut list packed into stock lengths so the buy list matches the cuts; prices with a cost total; and unlimited saved projects. No subscription and no account. Coming soon to iPhone and iPad.

How it works

1. Enter the width, depth and height. Feet and inches, decimals or 12' 6" all work.
2. Say whether the deck attaches to the house or stands on its own, and pick the lumber.
3. Read the drawing and the framing choices. Change any of them and watch the checks.
4. Open Materials for the full list, or Cuts for the first lines of the cut list.

Common questions

How far can a deck joist span?

It depends on the lumber size, the species and the spacing. Deck Planner shows the span table limit for the joist you pick and flags one that is past it, so you can change the size or the spacing before you buy.

How many footings does a deck need?

One under each post, and the post count follows the beam span and the deck size. The plan view shows every post and footing, and the material list counts the concrete bags for them.

Is the material list complete?

It covers the framing, footings, decking, hardware, stairs and railing for a straight, rectangular deck. Roofs, multi-level decks, curves and hot tubs are outside what the tool covers, and it says so rather than guessing.

Good to know

Deck Planner helps you plan and estimate. It is not engineering advice and it does not replace your building department, a licensed engineer or a contractor. Span and footing checks come from published prescriptive tables for typical conditions. Your town may use a different code edition, snow load, frost depth or soil value. Most decks need a permit. Check with your local permit office before you buy materials or build.

Nothing you type leaves your browser. There is no account and no tracking. Deck Planner is made by Commonwealth Business Systems LLC.