BDFT計算機の仕組み
Board foot（BF）は木材の体積単位で、144 in³（12 in × 12 in × 1 in）に相当します。本計算機は標準式を使用します：
- BF =（厚み（インチ）× 幅（インチ）× 長さ（フィート））÷ 12
- 複数本の場合： 合計BF = 1本あたりBF × 数量
入力すると値が即時更新されます。一般的な仕上げ寸法にはプリセットを使用してください（例：2×4 実寸 1.5 in × 3.5 in）。
Professional Lumber Calculator
BD FT 計算機
寸法を入力 — 結果は即時に更新されます。BF = (T in × W in × L ft) ÷ 12 を使用します。
W: 3.5"
T: 1.5"
L: 8ft
BD FT 計算機
寸法を入力 — 結果は即時に更新されます。BF = (T in × W in × L ft) ÷ 12 を使用します。
プリセット：
この断面の1フィートあたりBF：
—
Board Footとは？
1 board foot は 144 立方インチに相当する木材体積です。厚さ1インチの 1 ft² の面積、または 1/12 立方フィートとも考えられます。
多くの木材は「1×、2×」の呼び寸法で販売されますが、製材・プレーナー加工後は実寸が少し小さくなるため、多くの計算では実寸の厚みと幅を使います。
呼び寸法と実寸
呼び寸法 2×4 は、乾燥とプレーナー加工後に実寸で約 1.5 in × 3.5 in になります。BFの見積りでは実寸を使う方が現実的です。このツールのプリセットは一般的な仕上げ寸法を入力します。
1フィートあたりのBoard Feet — 一般的な実寸
長尺の見積りに便利（BF/ft = T × W ÷ 12）。
| サイズ（実寸） | 1フィートあたりBF |
|---|---|
| 1×4 (0.75″ × 3.5″) | — |
| 1×6 (0.75″ × 5.5″) | — |
| 1×8 (0.75″ × 7.25″) | — |
| 2×4 (1.5″ × 3.5″) | — |
| 2×6 (1.5″ × 5.5″) | — |
| 2×8 (1.5″ × 7.25″) | — |
| 2×10 (1.5″ × 9.25″) | — |
| 2×12 (1.5″ × 11.25″) | — |
Instant Results
Calculate board feet in real-time as you type dimensions
Accurate Formula
Uses standard BF = (T × W × L) ÷ 12 calculation
Cost Estimator
Get instant price estimates for your lumber needs
144 in³ per BF
12 BF per ft³
8+ Presets
Specialized Calculators
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Board Foot Calculator for Lumber
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Board Feet Calculator Philippines
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BD FT Formula
Understanding the mathematical foundation behind board foot calculations
The Basic Formula
BF = (T × W × L) ÷ 12
T = Thickness in inches
W = Width in inches
L = Length in feet
BF = Board Feet
Why Divide by 12?
One board foot equals 144 cubic inches (12″ × 12″ × 1″). When we multiply thickness (inches) × width (inches) × length (feet), we get a result in "inch²-feet". Dividing by 12 converts this to board feet, the standard unit for lumber volume.
Step-by-Step Example
1
Start with dimensions
2×4 board, 8 feet long
Actual: 1.5″ thick × 3.5″ wide × 8′ long
2
Multiply dimensions
1.5 × 3.5 × 8 = 42
3
Divide by 12
42 ÷ 12 = 3.5 BF
Result: 3.5 Board Feet
Board Foot Calculation Example
Common lumber calculations you'll encounter in projects
Deck Boards
Material: 5/4 × 6 decking
Actual Size: 1″ × 5.5″
Length: 12 feet
Quantity: 50 boards
(1 × 5.5 × 12) ÷ 12 = 5.5 BF
Total: 275 BF
Wall Framing
Material: 2×4 studs
Actual Size: 1.5″ × 3.5″
Length: 8 feet
Quantity: 100 studs
(1.5 × 3.5 × 8) ÷ 12 = 3.5 BF
Total: 350 BF
Hardwood Table
Material: 8/4 oak
Actual Size: 2″ × 8″
Length: 6 feet
Quantity: 8 boards
(2 × 8 × 6) ÷ 12 = 8 BF
Total: 64 BF
Board Foot Calculator Chart
Quick reference for common lumber sizes and their board foot values per linear foot
| Nominal Size | Actual Size | BF per Foot | BF per 8' | BF per 10' | BF per 12' |
|---|---|---|---|---|---|
| 1×4 | 0.75″ × 3.5″ | 0.219 | 1.75 | 2.19 | 2.63 |
| 1×6 | 0.75″ × 5.5″ | 0.344 | 2.75 | 3.44 | 4.13 |
| 1×8 | 0.75″ × 7.25″ | 0.453 | 3.63 | 4.53 | 5.44 |
| 2×4 | 1.5″ × 3.5″ | 0.438 | 3.50 | 4.38 | 5.25 |
| 2×6 | 1.5″ × 5.5″ | 0.688 | 5.50 | 6.88 | 8.25 |
| 2×8 | 1.5″ × 7.25″ | 0.906 | 7.25 | 9.06 | 10.88 |
| 2×10 | 1.5″ × 9.25″ | 1.156 | 9.25 | 11.56 | 13.88 |
| 2×12 | 1.5″ × 11.25″ | 1.406 | 11.25 | 14.06 | 16.88 |
Note: Values are based on actual (dressed) dimensions, not nominal sizes. Actual dimensions are slightly smaller due to planing and drying. Use these values for accurate material estimates.
How to Compute BD FT
Master the art of calculating board feet with our comprehensive guide
1
Using Inches & Feet
Most common method for lumber:
- Measure thickness in inches
- Measure width in inches
- Measure length in feet
- Multiply: T × W × L
- Divide result by 12
Example: (1.5 × 5.5 × 10) ÷ 12 = 6.875 BF 2
Using All Inches
Alternative method using inches:
- Measure thickness in inches
- Measure width in inches
- Measure length in inches
- Multiply: T × W × L
- Divide result by 144
Example: (1.5 × 5.5 × 120) ÷ 144 = 6.875 BF 3
Per Linear Foot Method
Quick calculation for long runs:
- Calculate BF per foot: (T × W) ÷ 12
- Multiply by total length in feet
- Multiply by quantity if needed
Example: (1.5 × 5.5) ÷ 12 = 0.6875 BF/ft
0.6875 × 10 ft = 6.875 BF Pro Tips
- ✓ Always use actual dimensions, not nominal sizes
- ✓ Add 10-15% waste factor for cuts and defects
- ✓ Round up to nearest whole number when ordering
- ✓ Keep a reference chart handy for common sizes
よくある質問
2x4x8 は何 board feet ですか？
実寸（仕上げ寸法）1.5″ × 3.5″ × 8′の場合 → (1.5 × 3.5 × 8) ÷ 12 = 3.5 BF。呼び寸法 2″ × 4″ × 8′の場合 → (2 × 4 × 8) ÷ 12 = 5.333 BF。
BDFt はどう計算しますか？
1メートルはわずかに長く、ヤードより約9.36%長いです。(1 m ≈ 1.0936 yd)
木材の 1000 board feet はどれくらいですか？
1,000 BF は MBF と呼ばれます。費用 = 1 BF あたりの価格 × 1000（樹種、等級、市場により変動）。
丸太の BDFt はどう計算しますか？
丸太は通常、Doyle / Scribner / International 1/4 などのルールでスケールし、末口径（樹皮内）と長さを使います。一貫した結果のために、地域で一般的なルール、または買い手の指定ルールを選んでください。