Workshop Calculators
The Math Behinda Better Build.
BenchRoot calculators handle the repetitive workshop arithmetic — board footage, stock layouts, sheet quantities, angles, spacing and measurement conversions — directly at the bench.
Works in the browser, on a phone at the bench. Fractions like 3/4 or 1 3/8 are accepted wherever a length is asked for.
Six instruments for the bench.
Calculation index
- 01Board Foot CalculatorEstimate rough lumber quantity.
- 02Stock Cut LayoutArrange repeated cuts across standard boards.
- 03Plywood EstimatorEstimate sheet quantity from rectangular parts.
- 04Miter AngleFind the cut angle for regular multi-sided frames.
- 05Equal SpacingLay out slats, spindles or dividers evenly.
- 06Fraction / Decimal / MetricConvert common shop measurements.
Calculator 01
Board Foot Calculator.
How much rough lumber to buy. A board foot is 144 cubic inches — one inch thick, twelve inches wide and twelve inches long.
Formula
bd ft = T × W × L × qty ÷ 144
purchase = bd ft × (1 + waste %)
One board foot = 1″ × 12″ × 12″ = 144 cu in
Net board feet
21.33bd ft
Waste allowance
+0.00bd ft
Purchase quantity
21.33bd ft
(1 × 8 × 96 × 4) ÷ 144 = 21.33 bd ft
Calculator 02
Stock Cut Layout.
Arrange repeated parts across standard-length boards, allowing a kerf between every cut.
Formula
board ≥ Σ parts + kerf × (cuts − 1)
longest part placed first
Boards required
2
Parts total
138in
Waste
54in
Waste share
28.1%
Suggested layout · 96″ boards
- Board 1A · A · B · C — offcut 5.625″
- Board 2B · B · C — offcut 47.75″
Parts are placed longest first, each on the first board with room for it and one kerf. This is a suggested layout from a quick rule of thumb, not a guaranteed minimum. Hatching marks the offcut.
Calculator 03
Plywood Estimator.
Estimate how many sheets a set of rectangular parts will need, from total area plus a waste allowance.
Formula
sheets = ⌈ Σ(W × L × qty) × (1 + waste %) ÷ sheet area ⌉
Raw area
46.31sq ft
With waste
53.26sq ft
Est. sheets
2
53.26 ÷ 32.00 sq ft per sheet = 1.66 → rounded up to 2
This is an area estimate. It does not account for grain direction, part orientation, kerf or exact nesting.
Blocks show area used per sheet, by part; hatching is the waste allowance.
Angles and spacing
Calculator 04
Miter Angle.
The cut for each corner of a regular frame — hexagons, octagons, picture frames.
miter = 180° ÷ n · interior = (n − 2) × 180° ÷ n
Each miter cut
30°
Interior corner
120°
Sides
6
Measured from square: set the saw to 30° and cut both ends of every piece.
Calculator 05
Equal Spacing.
Even gaps between slats, spindles, shelves or dividers, including both outside gaps.
gap = (opening − n × width) ÷ (n + 1)
Clear gap
5.6in
Centre to centre
7.6in
(36″ − 4 × 2″) ÷ 5 gaps · nearest 1/32″: ≈ 5 19/32″
Layout marks · left edge of each member, from the left side
- #15.6″
- #213.2″
- #320.8″
- #428.4″
Calculator 06
Fraction · Decimal · Metric.
Convert a shop measurement between fractional inches, decimal inches and millimetres.
Formula
1 in = 25.4 mm exactly
fractions rounded to the nearest mark
Fraction · 1/64″
5/16″
Decimal inches
0.3125″
Millimetres
7.9375mm
One inch, magnified · 1/64″ graduations
Measurement Reference
One inch, three ways.
The fractions that come up most at the bench, with their exact decimal and metric equivalents. 1 inch = 25.4 mm exactly.
| Fraction | Decimal inch | Millimetres |
|---|---|---|
| 1/16″ | 0.0625 | 1.5875 |
| 1/8″ | 0.125 | 3.175 |
| 3/16″ | 0.1875 | 4.7625 |
| 1/4″ | 0.25 | 6.35 |
| 3/8″ | 0.375 | 9.525 |
| 1/2″ | 0.5 | 12.7 |
| 5/8″ | 0.625 | 15.875 |
| 3/4″ | 0.75 | 19.05 |
| 7/8″ | 0.875 | 22.225 |
| 1″ | 1 | 25.4 |
Before the First Cut
Do the Math BeforeYou Cut the Wood.
A few seconds of arithmetic can save a board, a sheet or an entire glue-up.