Construction calculators that cite the code

Most trade calculators hand you a number and no reason to believe it. These ones name the standard, print the table, and show the work.

There is no shortage of construction calculators. Type almost any sizing question into a search engine and you will get a dozen results, most of them a form and a result and nothing else — no table, no code section, no statement of what load or service condition the number assumes. That last omission is the one that matters, because a span figure without its assumptions is not an answer. The same 2×10 spans one distance as a deck joist and a noticeably longer one as an interior floor joist, and a tool that does not say which it calculated has hidden the only decision in the problem.

Some of them are simply wrong. While building the deck beam page here, two of the highest-ranking deck calculators on the web disagreed with each other and with the actual values in IRC Table R507.5(1). One widely repeated figure put a Douglas fir-larch beam span 24% longer than the code allows — on a member that holds people several feet off the ground.

What is different here

Every page names its source and prints the table it reads from, in full, as real text you can search and copy. The worked example shows the arithmetic. The assumptions — live load, dead load, deflection limit, grade, wet or dry service — are stated rather than buried. And where a table stops applying, the page says so and stops, instead of quietly extrapolating past the edge of its own data.

Two things run automatically on every build. The visible table and the calculator's internal lookup come from a single source, so they cannot drift apart. And every figure quoted in the prose is executed against that data — if an edit makes a paragraph disagree with the table beneath it, the page does not publish. Where a value could not be verified against the code text itself, the page simply does not exist yet; several planned calculators are on hold for exactly that reason.

Who this is for

Pros who want the number and the citation and nothing in between, and homeowners who want the number plus enough plain explanation to trust it. Both should find the page readable without scrolling past an essay to reach the tool.

Nothing is sold here. No accounts, no sign-up, no quote forms. The calculators run entirely in your browser and nothing you type leaves it. The method, the full source list, and the traps found along the way are in Sources & Method.

Decking

5 calculators.

Structural

3 calculators.