Lumber Calculator

This page turns a pile of lumber into three numbers you can act on: how much wood the order contains in cubic meters, how much board there is end to end, and what it costs.

It is built around the way a supplier and a buyer talk about an order. Measure one board, say how many of them you need, and the three totals follow from that one piece. The same three totals also work the other way round, which is what makes the page useful when the quote arrives before the cut list: a volume, a running length or a budget can each be typed in to discover how many pieces it represents.

It suits deck boards, shelving and furniture stock, fencing, ceiling battens, beams and general timber orders. It does not care what the wood is for, only how big each piece is and how many there are, so it works the same for a single plank and for a delivery that arrives on a truck.

Five entries are enough: three measurements of one piece, how many you need, and what one of them costs.

A 3 m board, 150 mm wide and 25 mm thick

Twenty of these boards is the sort of order a small shelving or partition job needs. One piece first:

Then the whole order, at 9 USD a piece:

Everything on the page rests on one multiplication and one repeat: a board has a volume, and an order is that volume counted as many times as there are pieces.

The three dimensions must be on the same scale before they multiply, and the page handles that for you: a length in meters and a thickness in millimeters are brought to the same unit first. That is why the order of the boxes never matters, and why mixing the length and the width in different units gives the same volume as using one unit throughout.

The three totals

Volume and length answer different questions, and suppliers choose between them. Bulk timber and thicker sections are usually quoted by the cubic meter or by the cubic foot, because the price tracks how much wood is in the pile. Moldings, trim, battens and anything sold off a rack are often quoted by the running meter, where only the length matters. Filling in one price lets the page give you both, so you can compare a quote written either way.

What the volume units are worth

The volume menu spans nine orders of magnitude, and the middle of it is where lumber lives. A cubic meter is 1,000 liters, a liter is 1,000 cubic centimeters, and one cubic decimeter is exactly one liter. A single board is usually a small fraction of a cubic meter, which is why cubic centimeters or liters can be easier to read than a long decimal in cubic meters.

Lengths read independently of the volume

The total length box has its own length menu, so the same order can be quoted in meters while you read the volume in liters. The two are not linked by the menus: each shows the same underlying order in the unit you picked, and changing one never changes the other.

Every total is also an input. Type the figure you have been quoted and the page works out the piece count, or the price per piece, that it implies.

This is the fastest way to check a supplier’s arithmetic. A quote of 2.4 cubic meters for boards that each measure 0.012 cubic meters is 200 pieces, and the total length tells you whether that matches the run you planned. A quote of 300 USD against 8 USD a piece is 37.5 pieces, which is a quantity you can compare with what you actually need.

The most recent entry is the one that holds

When two entries disagree, the page cannot keep both. It keeps the number you typed last and recalculates an older one that sits in the same chain, so a figure you were sure about can change after you type a total. If a box should be recalculated instead, clear it first and then type the total; an empty box is always free to be solved.

Typing a total that already agrees with what the page has calculated changes nothing: the existing numbers simply stay as they were, and every box keeps its entered state.

Counts can come out fractional

The arithmetic is exact, so a budget rarely lands on a whole piece: 300 USD at 8 USD a piece is 37.5 pieces. That is a useful answer, not an error, because it tells you that 37 pieces leaves a little money over and 38 pieces goes slightly past the budget. Ordering still happens in whole pieces, and the fractional count is the honest middle of the two.

One forward: an order you are about to place. One backward: a quote you have been given and want to check.

The arithmetic is the easy part. What decides whether the totals match the delivery is what you measure and what the price is quoted against.

Working in inches and feet

The length boxes are metric: millimeters, centimeters, meters, kilometers, or meters and centimeters together. There is no inch or foot entry, so convert once and type the millimeters. The factors are exact definitions rather than rounded figures, $1\ \mathrm{in} = 25.4\ \mathrm{mm}$ and $1\ \mathrm{ft} = 304.8\ \mathrm{mm}$, so an 8 ft board is 2,438.4 mm with nothing lost.

A board measuring 1.5 in by 3.5 in by 96 in becomes 38.1 mm by 88.9 mm by 2,438.4 mm. Ten of them at 4.50 USD a piece come to 0.0825908 m3, 24.384 m and 45 USD. One board foot is 144 cubic inches, or about 0.00236 m3, so a quote written that way can be brought back to a cubic meter figure before you compare it.

Lumber that becomes a wall frame is counted by spacing rather than by volume, so a stud count for a run belongs in the framing calculator. Bring the answer back here once you have a piece count and a price.