Calculator Servicescalculatorservices.com
Construction

Lumber Calculator

Board-feet for a lumber order. Free online Lumber Calculator. Calculate lumber online — fast, accurate, mobile-friendly, no signup needed.

Board feet
106.666667

Derivation

  1. ├── 01Givenpieces = 20, t = 2, w = 4, l_ft = 8
  2. ├── 02Formulae.pieces × e.t × e.w × e.l_ft / 12
  3. ├── 03Substitutee.20 × e.2 × e.4 × e.8 / 12
  4. └── 04Compute Board feet106.666667
Did you know?

Every calculator here runs 100% in your browser — nothing is sent to a server or stored in a database.

§01What is

Understanding the Lumber Calculator

The Lumber Calculator computes Board feet from 4 inputs: pieces, thickness (in), width (in), length (ft). Board-feet for a lumber order.

On a construction site, estimates that come in 10% off add up to six-figure overruns. Running the quantities with a calculator instead of a rule-of-thumb gets you closer to the truth with zero extra effort. The Lumber Calculator sits in that toolkit — it board-feet for a lumber order. Enter your numbers above and the result updates instantly; every step of the math is shown in the Derivation panel so you can see exactly how the answer was reached.

§02The Formula

How it’s calculated

e.pieces × e.t × e.w × e.l_ft / 12

Where

pieces
Pieces
t
Thickness (in)
w
Width (in)
l_ft
Length (ft)
§03Practical Example

Step-by-step walkthrough

Scenario

Apply the formula to a realistic set of inputs: Pieces = 20, Thickness (in) = 2, Width (in) = 4, Length (ft) = 8.

  1. 01Start by noting the input — Pieces: 20.
  2. 02Start by noting the input — Thickness (in): 2.
  3. 03Start by noting the input — Width (in): 4.
  4. 04Start by noting the input — Length (ft): 8.
  5. 05Substitute these values into the formula: e.pieces × e.t × e.w × e.l_ft / 12
  6. 06Compute Board feet: the calculator returns 106.667.
  7. 07Cross-check the answer by opening the Derivation panel above — every line of math is shown so you can follow the computation end-to-end.
§04Variants

Common Lumber Problems

The formula gets rearranged depending on which variable you need. Here are the patterns you’ll run into in the real world — find the one that matches your problem and follow the worked steps.

01 · PATTERN

Pieces halved

pieces = 10 (from 20)

Keep every other input at its default and halve the pieces. See how board feet responds.

  1. 01New Pieces: 10
  2. 02Baseline Board feet: 106.667
  3. 03New Board feet: 53.3333
  4. 04Board feet decreases by 50% → use this sensitivity to plan for real-world variation.
02 · PATTERN

Pieces doubled

pieces = 40 (from 20)

Keep every other input at its default and double the pieces. See how board feet responds.

  1. 01New Pieces: 40
  2. 02Baseline Board feet: 106.667
  3. 03New Board feet: 213.333
  4. 04Board feet increases by 100% → use this sensitivity to plan for real-world variation.
03 · PATTERN

Thickness (in) halved

t = 1 (from 2)

Keep every other input at its default and halve the thickness (in). See how board feet responds.

  1. 01New Thickness (in): 1
  2. 02Baseline Board feet: 106.667
  3. 03New Board feet: 53.3333
  4. 04Board feet decreases by 50% → use this sensitivity to plan for real-world variation.
04 · PATTERN

Thickness (in) doubled

t = 4 (from 2)

Keep every other input at its default and double the thickness (in). See how board feet responds.

  1. 01New Thickness (in): 4
  2. 02Baseline Board feet: 106.667
  3. 03New Board feet: 213.333
  4. 04Board feet increases by 100% → use this sensitivity to plan for real-world variation.
§05FAQ

Frequently asked questions

Yes. The calculator implements the standard formula as documented and returns exact floating-point results. No approximations are used unless noted in the formula.
Your feedback

How useful was this calculator?

Your ratings stay in your browser — they help us learn which tools people actually rely on.

Rate it
Was this helpful?