Board Foot and Lumber Cost Calculator

The calculator turns a multi-row lumber tally into measured board feet, a user-adjusted purchasing quantity, and optional cost. Enter the thickness, width, length, and quantity printed on your tally or measured from the stock. It never silently converts nominal dimensions to actual dimensions, and it keeps material allowance and supplier rounding visible.

How to use this board-foot calculator

1. Select whether your dimensions are a rough/nominal tally basis or measurements of the actual stock.
2. Enter thickness and width in inches, length in feet, and the number of pieces. Fractions such as 1 1/4 are accepted.
3. Add a row for each different board size. Labels are optional and remain on your device.
4. Enter only the purchasing allowance you want to evaluate; zero is valid.
5. Enter the supplier’s tally increment and optional price per board foot.
6. Compare measured volume, allowance-adjusted need, and rounded purchase quantity before ordering.

Read the lumber measurement guide if you are unsure whether to enter rough, nominal, or actual dimensions.

Measurement guide

Measure thickness across the smallest face, width across the broad face, and length end to end. Record the basis the supplier uses. A quarters label is a rough-lumber naming convention: 4/4 corresponds to a one-inch tally thickness and 5/4 to 1.25 inches, but it does not guarantee the finished surfaced thickness. Use measured dimensions when you need physical volume from the board as it exists now.

Understanding the result

“Measured board feet” is the geometric total. “After allowance” applies your percentage without rounding. “Board feet to purchase” then rounds upward to the supplier increment you entered. If you supply a price, the purchasing cost uses that rounded purchase quantity—not a hidden or prematurely rounded value.

Methodology and formula

For each row:

board feet = thickness (in) × width (in) × length (ft) × quantity ÷ 12

The equivalent volume definition is 144 cubic inches per board foot. Row values are summed at full precision. The calculator then applies base × (1 + allowance/100) and rounds upward by ceil(raw order ÷ increment) × increment. Display rounding happens last.

Board feet are volume. This result does not determine grade, usable yield, moisture content, weight, structural suitability, or recoverable lumber from a log. Hardwood grading and log scales are separate systems.

Worked examples

One 1 × 6 × 8-foot board

1 × 6 × 8 ÷ 12 = 4 BF. With no allowance and a 1-BF supplier increment, the purchase quantity is 4 BF.

Ten 1 × 4 × 8-foot boards

The measured volume is 1 × 4 × 8 × 10 ÷ 12 = 26.667 BF. A 10% allowance produces 29.333 BF before supplier rounding; a 1-BF increment produces a 30-BF purchase tally.

Mixed tally and cost

One 1 × 6 × 8 board and one 2 × 8 × 10 board total 17.333 BF. With a 10% allowance, 1-BF increment, and a user price of $5/BF, the purchase quantity is 20 BF and the planning cost is $100.

Common mistakes and troubleshooting

• Do not mix inches and feet in the same field.
• Do not assume a quarters label is the surfaced thickness.
• Use whole numbers for piece quantity.
• Confirm whether a supplier prices the measured tally or a rounded purchasing increment.
• A board-foot answer cannot be used as a hardwood grade or log-yield result.

If a row is rejected, check that every dimension and the quantity are positive and that the length unit matches the number entered. If the total looks wrong by a factor of 12, recheck whether length was entered as feet or inches and whether thickness and width are the intended tally basis. A sudden jump in “board feet to purchase” is normally the explicit allowance or supplier-increment ceiling; compare the three result stages before changing the inputs. Exported labels are descriptive only and never change a row’s arithmetic.

Frequently asked questions

Is a board foot the same as a square foot?

No. A square foot measures area. A board foot measures volume: 144 cubic inches.

Should I use nominal or actual dimensions?

Use the same documented basis as the tally or purchasing workflow. Choose actual when calculating the physical volume of measured stock. The calculator records your choice but does not substitute dimensions.

Why is the purchase amount larger than the measured amount?

It can include two separate increases: your explicit allowance and upward rounding to the supplier increment. Both appear in the breakdown.

Can this estimate the weight of my boards?

Not without a basis-specific density and moisture model. The board-foot result is volume only.

Does the calculator grade lumber?

No. It does not implement NHLA rules, structural grades, or log scales.

Related workflow

• Use the deck board calculator when the job is laying out straight surface boards rather than tallying lumber volume.
• Export a clean row tally before requesting a supplier price.

Calculation engine: 1.0.0. Technical review: 2026-08-22. All calculations run locally in the browser.

References and further reading

These sources define or explain the calculation. Source editions and model limits are part of the result—not decorative citations.

1. NIST Handbook 44, Appendix C — General Tables of Units of Measurement, National Institute of Standards and Technology — Current edition; verify Appendix C in the linked edition; Appendix C, board-foot unit definition; accessed 2026-08-22. BF-01
2. Wood Handbook — Wood as an Engineering Material, USDA Forest Products Laboratory — FPL-GTR-282, 2021; Moisture, dimensions, and wood-property context; accessed 2026-08-22. BF-02