You pick up a “2×4” at the hardware store, grab a tape measure, and panic. It’s 1.5 inches by 3.5 inches. Did they short you? No. The label is lying, technically speaking. This is the difference between nominal and dressed dimensions, and it trips up almost every first-time DIYer.
Lumber is raw wood, but what you buy at the lumber yard is S4S material. That stands for “surfaced on four sides.” The mill planes down the rough bark and irregularities to create a smooth, uniform board. The nominal size (2×4, 1×6, etc.) refers to the wood before it got planed. The actual size is what’s in your hand after the planing.
If you’re cutting studs for a wall or framing a deck, you need to know the real numbers, not the marketing numbers. Using the wrong dimension can throw off your joist spacing, leave gaps in your subfloor, or make your fence posts look like they’re leaning when they’re not.
How to Read Lumber Sizes: Nominal vs. Dressed
The confusion stems from history. Lumber was cut from logs, and the size was estimated based on the raw timber. Once machinery got better, they planed the wood down for consistency, but the name stuck.
Here is the cheat sheet for the most common board (1x) sizes:
- 1×6 Nominal: Measures 3/4 inch thick by 5-1/2 inches wide
- 1×8 Nominal: Measures 3/4 inch thick by 7-1/4 inches wide
- 1×10 Nominal: Measures 3/4 inch thick by 9-1/4 inches wide
When you move up to dimension lumber (2x and 4x), the thickness drops to 1-1/2 inches across the board.
- 2×2 Nominal: 1-1/2 inch x 1-1/2 inch
- 2×4 Nominal: 1-1/2 inch x 3-1/2 inch
- 2×6 Nominal: 1-1/2 inch x 5-1/2 inch
- 2×8 Nominal: 1-1/2 inch x 7-1/4 inch
- 2×10 Nominal: 1-1/2 inch x 9-1/4 inch
- 2×12 Nominal: 1-1/2 inch x 11-1/4 inch
- 4×4 Nominal: 3-1/2 inch x 3-1/2 inch
Why does this matter? Say you’re building a shelf to fit inside a 36-inch wide cabinet. You think a 2×4 will work. It won’t. You have 3-1/2 inches of actual width, not 4. If you’re stacking multiple boards to build a platform, you’re losing 1/2 inch per board. That adds up fast
You need to know what you’re buying before you cut it.
Why Lumber Beats Plywood for Structural Framing
Plywood is great for sheathing, subfloors, and furniture. But when you are building a load-bearing wall, a roof truss, or a floor joist, solid lumber is the standard. It handles point loads better. A nail or bolt concentrates stress in one spot. Plywood distributes it across the layers. That can fail unevenly.
Solid wood is predictable. You know the grain runs one way. You know how it will split if you pre-drill wrong. You know how it will warp if it gets wet. Plywood is manufactured to be dimensionally stable, but it has its own failure modes. It layers can delaminate if the glue fails.
How to Choose the Right Grade for Your Project
Not all lumber is created equal. The stamp on the end tells you what you are getting.
- Selects: These are clean, straight, and free of major defects. Use them for trim, cabinet faces, or anything visible. They cost more.
- Common (Stud) Grade: This is what you use for framing walls, floors, and roofs. It has some knots, some twist, and some checking. It is cheap and strong enough. For a DIYer, this is the default choice.
- S4S (Surfaced Four Sides): The wood has been planed on all four sides. It fits together tightly. Buy this for any joinery or framing where fit matters.
- Rough Lumber: This comes straight from the sawmill. It is not planed. It is cheaper per board foot. You need a planer and a lot of time to make it usable. Most homeowners should skip this unless they are building a cabin from scratch.
Which Tools Do You Actually Need to Cut It?
You don’t need a fancy table saw. But you need something that makes a straight cut.
- Circular Saw: Your workhorse. Use a sharp blade. For 2×4 framing lumber, a 7-1/4 inch blade is fine. For thicker stock, go bigger. Support the piece from both sides. Let the saw do the work. Don’t force it.
- Miter Box: Great for short, precise cuts. Cheap. Effective for trim work.
- Jigsaw: Not for framing. Use it for curves, cutouts, and intricate shapes. It leaves a rough edge. You will need to sand it.
Safety First: Eye Protection is Non-Negotiable
Wood dust is a known carcinogen. It gets into your lungs. It gets into your eyes. It gets into your nose.
Wear safety glasses. Not sunglasses. Safety glasses. If you are cutting a lot, wear a respirator with a P100 filter. A dust mask from the hardware store won’t stop fine particulate matter.
Also, keep your hands away from the blade. Use a push stick for narrow pieces. Never reach across the path of the blade to grab a falling piece of wood. Let it fall. Pick it up later.
Where to Buy Lumber Without Getting Ripped Off
Home centers are convenient. They are also inconsistent. One store might have dry, straight lumber
