Lumber Calculator

Compute board feet, volume, number of boards, or total cost from lumber dimensions. Supports nominal-size presets or actual dimensions.

Practical Guide

Lumber Calculator: Fast Board-Foot, Linear-Foot, and Piece Counts

Estimate lumber for framing, decking, trim, and furniture without guesswork. This guide mirrors the calculator below it—choose a method, enter sizes, add waste, and convert between board feet, linear feet, pieces, and cost in seconds.

8–11 min read Updated November 10, 2025

Quick Start

  1. 1 Select a calculation mode that matches your task: Board Feet (hardwood, milling), Linear Feet (trim, framing by length), or Coverage (decking/fencing by area).
  2. 2 Enter the actual sizes (thickness × width × length). For hardwoods use quarters (4/4, 5/4, 8/4). For framing, the calculator handles nominal vs actual automatically.
  3. 3 Add a waste allowance (typically 10–15% for furniture hardwoods, 5–10% for framing and decking).
  4. 4 If pricing is known, input price per board foot or price per linear foot to get cost.
  5. 5 Use unit toggles to switch between in/ft and mm/m; the calculator converts for you.

Tip: For mixed lengths, enter each length line as a separate item. The calculator will sum totals and apply waste globally so you don’t over-pad each piece.

Watch-out: Board feet use actual thickness and width. A “2×4” is not 2 in × 4 in (it’s 1.5 in × 3.5 in). Verify your inputs before ordering.

Choosing Your Method

Method A — Board Feet (BF)

Best for hardwood projects, milling, and rough-sawn stock priced by board foot.

  • Matches how hardwood dealers quote.
  • Works with mixed lengths and thicknesses (4/4, 5/4, 8/4).
  • Converts easily to volume and cost.
  • Requires actual dimensions; nominal sizes will overstate.
  • Less intuitive for long runs (trim, fascia).
\( \text{BF}=\dfrac{T_{\text{in}}\times W_{\text{in}}\times L_{\text{ft}}}{12} \)

Method B — Linear Feet (LF) & Piece Count

Best for framing, trim, fence rails, and decking where length drives purchase.

  • Great for standard stock lengths (8, 10, 12, 16 ft).
  • Priced by linear foot at many yards.
  • Simple add-up across sizes.
  • Doesn’t capture thickness/width changes into a single metric.
  • Cost comparison to BF-priced stock needs conversion.
\( \text{LF total}=\sum L_i \quad;\quad \text{Cost}=\text{LF}\times \text{price/LF} \)

Need to cover an area (deck or fence)? Use coverage mode: it multiplies boards per course and courses to reach total length, then converts to pieces and LF automatically.

What Changes Your Totals the Most

Actual vs. nominal size

Nominal “2×” lumber is smaller in actual dimensions (e.g., 2×4 → 1.5 in × 3.5 in). Using nominal in BF will overorder.

Thickness category

Hardwoods use quarters: 4/4≈1 in, 5/4≈1.25 in, 8/4≈2 in. BF scales linearly with thickness.

Length mix

Odd lengths create trim waste. Group by length to optimize cuts and reduce offcuts.

Moisture & grade

KD vs. PT vs. green changes weight, warp risk, and defect allowance. More defects → higher waste %.

Kerf, knots & straightness

Every rip loses kerf; knots and bows reduce yield. Add 5–10% waste for heavy trimming.

Coverage assumptions

Decking and siding need gaps/overlaps. The calculator uses effective cover width so totals reflect reality.

Variables & Symbols

  • BF Board feet
  • LF Linear feet
  • T Thickness (in or mm)
  • W Width (in or mm)
  • L Length (ft or m)
  • n Pieces (count)
  • p Price (per BF or per LF)
  • w% Waste fraction (e.g., 0.10)

Worked Examples

Example 1 — Hardwood Project (Board Feet & Cost)

  • Stock: 4/4 (≈1 in) × 6 in boards, lengths 8 ft
  • Quantity: 20 pieces
  • Waste: 12% (mill defects, grain matching)
  • Price: \$7.50 per BF
1
Board feet per piece: \( \dfrac{1\times 6\times 8}{12}=4 \,\text{BF} \)
2
Before waste: \( 20\times 4=80 \,\text{BF} \)
3
Add waste: \( 80\times (1+0.12)=89.6 \,\text{BF} \Rightarrow \text{order }90 \,\text{BF} \)
4
Estimated cost: \( 90\times \$7.50 = \$675 \)

The calculator mirrors this: enter T, W, L, n, set waste %, and (optionally) price per BF to get total BF and cost.

Example 2 — Metric Framing (LF, m, and BF Conversion)

  • Stock: 50 × 100 mm studs (≈ actual 45 × 95 mm), length 3.6 m
  • Quantity: 60 pieces
  • Waste: 8%
1
Total length: \( 60 \times 3.6 = 216 \,\text{m} \) (≈ 709.3 ft LF)
2
Volume per piece: \( 0.045\times 0.095\times 3.6 = 0.01539 \,\text{m}^3 \)
3
Total volume: \( 60\times 0.01539 = 0.9234 \,\text{m}^3 \)
4
Board feet (optional): \( 1\,\text{BF}=0.0023597\,\text{m}^3 \Rightarrow \frac{0.9234}{0.0023597}\approx 391 \,\text{BF} \)
5
Add waste: \( 391\times (1+0.08)\approx 422 \,\text{BF} \) (useful for price comparisons)

The calculator converts between metric and imperial automatically. Toggle units to confirm both views.

Project Types & Variations

Different projects change how you measure, price, and apply waste. Use this table as a quick guide before ordering.

Project / MaterialHow to EstimateTypical WasteNotes
Framing (2× lumber)Linear feet or piece count by standard lengths5–8%Use actual sizes for BF; spacing drives count (e.g., studs at 16 in o.c.).
Decking (5/4×6, 2×6)Coverage: deck width ÷ effective board width × deck length8–12%Include gaps (≈1/8–3/16 in) and starter/finish boards.
Fencing (pickets, rails)Coverage (pickets) + LF (rails/posts)8–12%Gate framing and post spacing often add extras; confirm post depth.
Hardwoods (furniture)Board feet by T×W×L per piece10–15%Increase waste for figure matching, knots, or resawing.
Trim & mouldingsLinear feet per room + cuts/joints10–12%Inside/outside corners and scarf joints increase offcuts.
Posts & beams (4×, 6×)Pieces by length; optional BF for cost compare5–8%Heavier sections are sold by piece or LF; check grade & species.

Buying, Logistics & Checks

Selection Criteria

  • Species & grade: Match strength, appearance, and price (SPF, DF, SYP, oak, maple, etc.).
  • Moisture: KD for interior stability; PT for exterior durability.
  • Actual sizes: Confirm surfaced (S4S) vs rough; hardwoods often sold rough.
  • Length availability: Prefer lengths that minimize offcuts for your cut list.

Logistics & Handling

  • Inspect for bow, cup, twist; pick straight stock for long runs.
  • Stack with stickers for airflow; acclimate interior lumber before milling.
  • Transport long pieces with support at multiple points to prevent damage.

Sanity Checks

  • Cross-check LF vs BF totals for the same order to avoid unit surprises.
  • Re-run with ±5% waste to see budget sensitivity.
  • Compare cut list yield to stock lengths to reduce kerf losses.
  • Use actual dimensions in BF math: \( \text{BF}=\frac{T_{\text{in}}W_{\text{in}}L_{\text{ft}}}{12} \).
  • Include kerf for rips/crosscuts (e.g., 1/8 in per cut).
  • Increase waste for complex joinery or color/figure matching.
  • For exterior projects, account for spacing, overlaps, and code requirements.

Frequently Asked Questions

What is a board foot and how do I calculate it?
A board foot (BF) is a volume measure equal to 1 in × 12 in × 12 in (144 in³) or 1/12 of a cubic foot. Use \( \text{BF}=\dfrac{T(\text{in})\times W(\text{in})\times L(\text{ft})}{12} \). Always use actual, not nominal, dimensions.
How much waste should I add?
Typical ranges: 5–8% for framing, 8–12% for decking/fencing, and 10–15% for furniture hardwoods. Increase waste for knots, figure-matching, short offcuts, or heavy milling.
What’s the difference between nominal and actual sizes?
Nominal sizes (e.g., 2×4) are historical labels; surfaced lumber is smaller (≈1.5 in × 3.5 in). The calculator uses actual sizes for BF math and lets you pick nominal for convenience where appropriate.
Can I compare price per BF and price per LF?
Yes. Convert LF to BF by multiplying LF by \( \dfrac{T(\text{in})\times W(\text{in})}{12} \). Then compare apples-to-apples on cost.
How do I estimate studs for a wall?
Find wall length in inches, divide by on-center spacing (e.g., 16 in), add one stud per layout line, and add 3–4 extra for openings and corners. The calculator’s piece mode can sum totals by length.
How do metric units convert to board feet?
\(1\,\text{BF}\approx 0.0023597\,\text{m}^3\). Multiply cubic meters by 424 to approximate BF, or let the calculator toggle between m, mm and ft, in for you.
Does the calculator handle coverage (decking/siding)?
Yes. Enter project area and effective board width (actual width minus gap/overlap). The tool returns pieces, LF, and—if you supply pricing—cost.
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