Board Foot & Timber CFT Calculator
Lumber volume and cost in board feet, CFT or m³ — and round logs by Hoppus.
Lumber and timber
No pieces — add a row, or measure only round logs below.
Round logs optional
Measured at mid-length, under the bark. Volumes by the Hoppus (quarter-girth) formula and the true round volume.
Volume by row
| Item | Pieces | Board feet | CFT | m³ | Cost |
|---|
Round logs
| Logs | Count | Hoppus ft³ | Hoppus m³ | True m³ | Cost |
|---|
Hoppus volume = (girth ÷ 4)² × length, 78.54 % of the true round volume girth² × length ÷ 4π.
About the Board Foot & Timber CFT Calculator
Add up a list of lumber or timber — studs, joists, boards, battens, beams — and get its volume in board feet, in the cubic feet (CFT) the Indian timber trade uses, and in cubic metres, with the cost at whatever rate you are quoted: per board foot, per CFT, per m³, per piece or per running foot or metre. Round logs are measured too, by the Hoppus (quarter-girth) formula used to sell round timber, next to their true volume.
US softwood lumber is sold by its nominal size — a 2×4 is billed as 2 in × 4 in but is dressed to 1½ × 3½ in — so for nominal pieces the tool shows both the board feet you pay for and the wood you actually get. Work in feet and inches or in millimetres and metres; everything stays on your device.
How to use it
- Choose feet & inches or metric. Each row is one kind of piece: how many, the thickness, width and length (
2,4and8for 2×4s 8 ft long; fractions such as1 1/2and lengths such as8' 6"work). - In feet and inches, say whether the size is nominal (US softwood lumber such as a 2×4) or actual (measured, hardwood, rough-sawn or Indian sizes).
- Optionally type a price for the row and what it is per: board foot, CFT, m³, piece or running length. Rows without a price still count in the volumes.
- For round logs, add a row with the girth (circumference) at mid-length — or switch to diameter — and the length, and optionally a price per Hoppus ft³, Hoppus m³, true m³ or log.
- Read the totals, check each row in the table, then copy the list or download it as CSV.
Examples
10 × 2 × 4 × 8 ÷ 12 = 53.33 board feet billed (4.44 CFT, 0.1259 m³) · dressed 1½ × 3½ in, so 0.0826 m³ of wood
20 × 10 × 4 × 2 ÷ 144 = 11.11 CFT (133.33 board feet, 0.3146 m³) · priced per CFT, the cost is 11.11 × the rate
10 × 0.05 × 0.1 × 3 = 0.15 m³ = 63.57 board feet = 5.30 CFT · 30 running metres
(60 ÷ 4)² × 12 ÷ 144 = 18.75 Hoppus ft³ (0.531 Hoppus m³) · true volume 0.676 m³ (23.87 ft³) — the Hoppus figure is 78.5 % of it
The formulas
- Board foot: the volume of a board 1 ft long, 1 ft wide and 1 in thick — 144 in³ (NIST Handbook 130, Method of Sale §2.12.1.1). Board feet = thickness (in) × width (in) × length (ft) ÷ 12.
- CFT: length (ft) × width (in) × thickness (in) ÷ 144 — the same as board feet ÷ 12.
- m³: thickness × width × length in metres. 1 board foot = 0.00236 m³ (423.78 board feet per m³); 1 ft³ = 0.02832 m³ (35.31 ft³ per m³).
- Hoppus (quarter-girth): (mid-length girth in inches ÷ 4)² × length in feet ÷ 144 = Hoppus cubic feet; in metric, (girth in m ÷ 4)² × length in m. A Hoppus ton is 50 Hoppus ft³ (FAO, ITTO and UN, Forest product conversion factors, §2.1.3.2).
- True volume of a log (from the mid-length girth G): G² × length ÷ 4π, the volume of a cylinder of that girth.
Nominal and actual sizes
US softwood lumber is named by nominal sizes taken from the rough board before it was dressed. Dry lumber made to the American Softwood Lumber Standard (PS 20) is dressed to: thickness 1 → ¾ in, 2 → 1½ in, 3 → 2½ in, 4 → 3½ in; width 2 → 1½ in, 3 → 2½ in, 4 → 3½ in, 6 → 5½ in, 8 → 7¼ in, 10 → 9¼ in, 12 → 11¼ in (as tabled in NIST Handbook 130 §2.10). Board-foot prices for such lumber are normally on the nominal size, so choose nominal to match the bill; the tool adds the dressed volume. Hardwood, rough-sawn and metric timber is measured at its actual size — choose actual.
Why Hoppus is smaller than the true volume
The Hoppus formula treats a quarter of the girth as the side of a square, so it always gives π ÷ 4 = 78.54 % of the volume of the round log measured the same way (FAO, §2.1.3.2). That is why a Hoppus foot of round timber is not a cubic foot of wood: compare quotes only in the same measure. Measure the girth at mid-length, under the bark unless the seller measures over it.
Limitations
- Volumes are of the sizes you enter. Saw kerf, offcuts, defects and drying shrinkage are not deducted — add spare pieces yourself.
- The dressed sizes cover nominal 1 to 4 in thick and 2 to 12 in wide (PS 20 dry sizes); for other nominal sizes enter the actual size.
- Log volume uses one girth at mid-length. Tapered or crooked logs, and trade rules with their own allowances for bark or defects, give different figures.
- Prices are whatever you type; no market rates are built in.
Privacy
Everything happens in your browser. What you enter or open here is not uploaded or stored by MySmartCoPilot.
Frequently asked questions
How many board feet are in a 2×4?
A nominal 2×4 has 2 × 4 ÷ 12 = 0.667 board feet per foot of length: 5.33 for 8 ft, 6.67 for 10 ft and 8 for 12 ft. The actual dressed board (1½ × 3½ in) holds about 66 % of that wood (5.25 of 8 square inches).
How do I calculate the CFT of wood?
Multiply the length in feet by the width and thickness in inches and divide by 144. A 10 ft piece 6 in × 2 in is 10 × 6 × 2 ÷ 144 = 0.833 CFT. For a round log, use the Hoppus formula: (girth in inches ÷ 4)² × length in feet ÷ 144.
How many board feet are in a cubic foot or a cubic metre?
12 board feet in a cubic foot, and 423.78 board feet (35.31 cubic feet) in a cubic metre.
What is the Hoppus formula?
A way of measuring round timber: (girth at mid-length ÷ 4)² × length. With the girth in inches and the length in feet, divide by 144 to get Hoppus cubic feet. It gives 78.54 % of the log's true volume.
Should I enter the nominal or the actual size?
Use the size the seller prices by. US lumber yards quote softwood by nominal size (a 2×4), so choose nominal; the tool still shows the dressed wood. For hardwood, rough-sawn timber and metric or Indian sizes, enter the measured size as actual.