What is the actual size of a 2×4?
A 2×4 actually measures 1-1/2 × 3-1/2 inches (about 38 × 89 mm) once it is dried and planed. An 8 ft 2×4 is billed as 5.33 board feet but holds 3.5 board feet of wood.
How to work it out
- Nominal 2×4 → dressed dry to 1-1/2 × 3-1/2 in (PS 20 standard sizes)
- Billed: 2 × 4 × 8 ft ÷ 12 = 5.33 board feet · Actual: 1.5 × 3.5 × 8 ft ÷ 12 = 3.5 board feet (66%)
The name is the rough, green size; drying and planing take off the rest. Every framing layout assumes the 3½ in width — it is why wall cavities are 3½ in deep and why two 2×4s nailed together make a 3 in post, not 4 in.
Adjust for your project
More options: L · Qty
- Actual thickness (decimal)
- 1.5 in
- Actual width (decimal)
- 3.5 in
- Board feet (nominal — what a board-foot price is charged on)
- 5.33 board feet
- Board feet (actual volume)
- 3.5 board feet
- Wood you get vs. what you pay for (if priced by the board foot)
- 66%
- Actual volume
- 0.292 cu ft
- Green (unseasoned) and rough-sawn lumber is larger than these dry, surfaced sizes. Pressure-treated lumber is often sold wet and shrinks slightly as it dries.
A 2×4 at stud and board lengths
| Length | Board feet (nominal — what a board-foot price is charged on) | Board feet (actual volume) | Actual volume |
|---|---|---|---|
| 92-5/8 in (precut stud) | 5.15 board feet | 3.38 board feet | 0.281 cu ft |
| 8 ft | 5.33 board feet | 3.5 board feet | 0.292 cu ft |
| 104-5/8 in (precut stud) | 5.81 board feet | 3.81 board feet | 0.318 cu ft |
| 10 ft | 6.67 board feet | 4.38 board feet | 0.365 cu ft |
| 12 ft | 8 board feet | 5.25 board feet | 0.438 cu ft |
| 16 ft | 10.67 board feet | 7 board feet | 0.583 cu ft |
What to know about a 2×4’s actual size
- Walls are built around 3½ in. Insulation batts for 2×4 walls are made 3½ in thick, and electrical boxes and window jambs are sized for that depth plus the wall finishes. A 2×4 wall is never 4 in of framing.
- Precut studs make the height work. A 92-5/8 in stud plus a bottom plate and a doubled top plate (three × 1½ in) frames a wall 97-1/8 in tall — room for an 8 ft ceiling after drywall. 104-5/8 in studs do the same for 9 ft walls.
- Stacking adds up in 1½ in steps. Two 2×4s face to face are 3 × 3½ in; three are 4½ × 3½ in. Size post brackets and pocket-hole or dowel layouts on those numbers, not on “4 × 4”.
- Metric match. At 38 × 89 mm, a 2×4 is the same section as the CLS studs sold in the UK.
For pricing, a 2×4×8 still counts as 5.33 board feet. The same 1½ in thickness runs through the actual size of a 2x6.
Different size? Use the full Lumber Dimensions Calculator.
What you’ll need
- 25 ft tape measureBudget price
A 25 ft tape with a stiff blade and a readable 1/16 in scale covers everything from cut lists to deck layout.
See options on Amazon (opens in a new tab) - Speed square (7 in)Budget price
Marks square and angled crosscuts and doubles as a saw guide for a circular saw. The degree scale is handy for rafters and stair angles.
See options on Amazon (opens in a new tab) - Digital calipersBudget price
For measuring actual board and plywood thickness to the thousandth — useful for sizing dadoes and checking planed stock.
See options on Amazon (opens in a new tab)
As an Amazon Associate we earn from qualifying purchases. Links to products are affiliate links — they cost you nothing extra and help keep these calculators free.
Frequently asked questions
What is the actual size of a 2×3?
A 2×3 measures 1-1/2 × 2-1/2 inches (about 38 × 64 mm).
What is the actual size of a 2×2?
A 2×2 measures 1-1/2 × 1-1/2 inches (about 38 × 38 mm) — the same 1½ in thickness on both faces.
How much wood is really in ten 2×4×8 studs?
Ten 2×4×8s are billed as 53.33 board feet but hold 35 board feet of wood — 66% of the nominal figure.
Other common sizes
- What is the actual size of a 4x4 — 3-1/2 × 3-1/2 in
- What is the actual size of a 2x6 — 1-1/2 × 5-1/2 in
Sources
- NIST, Voluntary Product Standard PS 20-20, American Softwood Lumber Standard (Rev. 1, 2021) (opens in a new tab) — Table 3: minimum dry and green dressed sizes of boards, dimension and timbers (timbers 5 in and thicker: 1/2 in under nominal, green).
- National Hardwood Lumber Association, Rules for the Measurement & Inspection of Hardwood & Cypress (2019) (opens in a new tab) — Paragraph 14: standard surfaced (S2S) thicknesses — 4/4 to 13/16 in, 5/4 to 1-1/16, 6/4 to 1-5/16, 8/4 to 1-3/4, 12/4 to 2-3/4.
- American Hardwood Export Council, The Illustrated Guide to American Hardwood Lumber Grades (opens in a new tab) — Rough quarter thicknesses and the 3/16 in / 1/4 in surfacing allowance.
- NELMA, Standard Grading Rules, Section 4: Other Board Grades (2024) (opens in a new tab) — Standard Shop thicknesses: 5/4 surfaced to 1-5/32 in.