How to Estimate Deck Materials on Your Phone

Two dimensions — how long the boards run, and how far the joists span — are enough to estimate a whole deck. This guide covers the framing, the boards, the footings, and the stain, and starts with the question everyone asks first.

Can you LiDAR-scan a deck?

No, and it's worth explaining why rather than letting you waste an afternoon finding out. Two independent reasons:

• Room scanning needs walls. Apple's RoomPlan builds a room from wall planes meeting at corners. An open deck has neither, so the scan never establishes a shape to work from.
• LiDAR doesn't like the outdoors. The sensor reaches about 5 metres, which a 16-foot deck already exceeds — and it works by reading its own infrared reflections, which direct sunlight washes straight out.

What you can do is measure it with the camera, which is a different thing from scanning it. You get the footprint — area and perimeter — rather than a 3D model, and that footprint is exactly what the take-off below needs.

Measuring the deck

Open Tools ▸ Measure a Surface, stand at one corner and tap it, then walk the edge tapping each corner as you go. Three corners minimum; an L-shaped deck is just more taps. Area and perimeter update as the shape closes.

Don't reach for Measure a Site here. Tracing on satellite imagery is the right tool for a lawn or a whole property, but aerial photography is roughly half a metre per pixel — a 3 × 4 m deck is about ten pixels across, which isn't something you can trace accurately. The camera also sees what's there today, so it works on a deck built since the last flyover, or one hidden under tree canopy.

Two things to know about the camera method. It wants texture and light: wood grain, board joints, and pavers track well, while smooth fresh concrete in flat light gives it very little to lock onto — the app tells you when it can't get a fix rather than quietly guessing. And it's for surfaces up to about 10 metres across; past that, tracking drift accumulates enough to matter and the app says so. A tape is still the answer when a number has to be exact.

Framing and boards

The Deck Frame calculator in BeaverPlot takes the length (the direction your boards run), the width (the direction joists span), and your joist spacing — 12, 16, or 24 inches on centre. It returns joist count and total joist length, rim joists, mid-span blocking where the span calls for it, and the decking itself in rows, linear feet, and boards to buy.

Footings

Deck footings are round forms, not slabs, so the usual length × width × depth doesn't apply. Volume is π × (diameter ÷ 24)² × depth in feet. The Concrete calculator has a Footings mode that takes the form diameter (8, 10, or 12 inches), the depth, and how many you're pouring, and gives you bags.

As a sanity check: a 10-inch form 42 inches deep takes about four 80 lb bags. A 12-inch form at 48 inches takes about six.

Stain

The variable that catches people out is the wood, not the product. Deck Stain asks for the condition because it changes coverage by roughly a factor of two: new smooth decking takes around 300 sq ft per gallon, while weathered, greyed, porous boards drink closer to 150. Estimate a tired deck at the new-wood rate and you'll run out halfway through.

What these numbers are

A starting take-off, not a plan. Joist size, beam spans, and footing depth are engineering decisions driven by load, species, and local code — the calculators quantify the materials once those are settled, they don't settle them. And order to the next whole unit: railing spindles, end grain, and rough-sawn faces all take more stain than a flat surface, and running short mid-job costs a trip.

Every calculator here is free, and none of them need a scan or a LiDAR phone.

Get BeaverPlot. If the deck isn't built yet, start by measuring the space from your phone.