Nominal ≠ Actual

A 2×4 isn't 2 inches by 4 inches.

The real dimensions behind every nominal size — lumber, fasteners & pipe, free and instant.

Pick a size below and see what it actually measures — no login, no scratch pad.

NOMINAL 4" ACTUAL 3½" ½" lost to milling + drying
DASHED = WHAT IT'S CALLED · SOLID = WHAT YOU GET

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LUMBER, FASTENERS & PIPE

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TAP A SIZE FOR ITS ACTUAL DIMENSIONS
Nominal Size (what it's called)
2×4
Actual Size (what you measure)
1½" × 3½"

View full guide & calculators for this size →

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Project calculators

USES ACTUAL DIMENSIONS, NOT NOMINAL

Deck board coverage

How many boards to cover a given deck area, accounting for actual board width and gap spacing.

Board feet calculator

Uses actual thickness and width to compute true board feet for pricing or ordering.
Got a whole list of cuts for a project? The Cut List Optimizer figures out the fewest boards to buy and exactly what to cut from each one.
Building steps or a deck? The Stair Calculator works out riser height and stringer length, and the Deck Span Estimator gives you a rough joist-span ballpark.
Pouring post holes or a footing? The Concrete Bag Calculator works out how many bags to buy. Converting a tape-measure reading? The Fraction to Decimal Converter handles fractions, decimals, and millimeters.

Full reference chart

DIMENSIONAL SOFTWOOD LUMBER · INCHES
Nominal SizeActual SizeActual (decimal)