Reference Charts

Quick reference tables for the numbers you look up over and over. All dimensions are actual milled sizes, not nominal names.

Charts and tables

• Nominal vs actual chart1x2 to 8x8, milled dimensions
• Board foot price chartCost per board foot by species
• Lumber weight chartPounds per board foot and per cubic foot
• Plywood sizes4x8, 5x5 and metric sheets
• Deck board spacingGaps by board width and span
• Joist span table2x6 to 2x12 at 12, 16 and 24 in OC
• Stair rise & runIRC riser and tread limits
• Fastener chartGauge, length and pilot hole size
• Miter angle chartSaw settings from 30 to 150 degrees
• Species weightJanka hardness and durability

How to use these tables

Each chart answers a question that comes up on every project, and each one is built the same way: the left column is what you order, the right columns are what you actually get. Look up the nominal name you see on the price tag, then read across to the milled dimension before you do any arithmetic. Doing it the other way round is how a material list ends up short by a board or two.

Print the ones you use most. A joist span table and a nominal-size chart on the wall of the shop will save more trips to the computer than any app.

Where the numbers come from

• Milled dimensions follow the voluntary product standard for softwood lumber. The shrink from green to dried stock is what turns a 2 inch board into 1.5 inches, and it applies to every species sold in North America.
• Joist spans come from the span tables in the International Residential Code, using SPF (spruce-pine-fir) values at 10 psf dead load and 40 psf live load, which is the standard residential floor and deck loading.
• Stair dimensions follow IRC R311.7: maximum riser 7.75 inches, minimum tread 10 inches, with the tighter 7.25 inch riser limit above about 151 inches of total rise.
• Species hardness is the Janka ball test, which measures the force required to embed a steel ball halfway into the wood. Higher is harder, and it is a decent predictor of how a floor or a bench top will wear.
• Lumber weight is given at a nominal 12 percent moisture content, which is close to what kiln-dried framing lumber settles at in service.

Three things people misread

• Nominal is not actual. A 2x4 is 1.5 by 3.5 inches. Any coverage calculation built on the nominal name overstates the board by about 8 percent, which over a deck is dozens of boards.
• A span table is not a suggestion. The values are maximums for the stated loading, species and spacing. Change any one of those and the row you read no longer applies.
• Board feet measure volume, not area or length. Two boards with the same board footage can cover very different areas depending on their width.