Reference Charts
The tables our calculators run on, published in full. Every figure here is the same value the tools use — they are generated from one source, so a chart and a calculator on this site cannot disagree with each other.
- Roof Pitch Chart Roof pitch conversion chart from rise-over-12 to degrees and percent slope, with the area multiplier and what each slope can be roofed with.
- Lumber Dimensions Chart Nominal versus actual dimensions for standard framing and board lumber, in inches and millimetres, with the rule behind the difference.
- Concrete Bag Chart How many bags of concrete make a cubic yard by bag size, coverage for common slab and post hole dimensions, and where bagged mix stops making sense.
- Sheet Goods Chart Gypsum board thickness and weight, sheet sizes and coverage per 1,000 square feet, and the ceiling framing limit that decides which board you can use.
Why publish the tables at all
A calculator answers one question with one set of inputs. A table lets you see the shape of the whole thing — how ampacity changes across every conductor size at once, or what happens to a derating factor as ambient temperature climbs. Both are useful and they are useful at different moments.
There is also a practical reason. On a job site with no signal, a printed chart works and a web form does not.
These are generated, not transcribed
Every row on these pages is produced from the same data the calculators use. Change a value in the conductor table and the AWG chart, the conduit fill chart and the wire size calculator all change together, because there is one table rather than three copies of it.
That matters more than it sounds. A site where the chart says one thing and the calculator says another has quietly destroyed the only reason to trust either, and hand-maintained tables drift apart the moment anything is updated.
Verify before you rely on them
Code tables change between editions and local amendments frequently differ from the model codes. The figures here are current to the best of our knowledge and cited by section, but for anything safety-critical, check them against your own code book or a licensed professional. Each chart lists its sources for exactly that reason.