About this site
Construction calculators that show their source
MyBuildingCalculators.com is 58 free construction calculators for US residential work, built and maintained by Syed Zulqarnain. Every structural result names the exact code table it was read from, so you can check it against the code book instead of trusting a number on a screen.
Most span tables online are copied from a copy of a copy, and by the third pass somebody has dropped a footnote about deflection limits or wet-service factors that changes the answer. Catching that is most of what Zulqarnain does here.
He built this site because the calculators he kept finding either hid their source or had none. Every structural tool on it cites the specific table it draws from, IRC 2021 Chapters 5, 6 and 8, with the AWC DCA 6 guide used only for deck footing sizes, and the methodology page shows the rounding rules so anyone can check the math.
He is not a structural engineer and the site does not pretend otherwise. What it does is reproduce published code tables without editorializing, flag every assumption an input makes, and tell you when a span falls outside the table instead of guessing. Anything past that is a job for a licensed engineer and your local inspector, and the the disclaimer says so.
Zulqarnain has spent six and a half years building and ranking sites for remodeling and construction businesses across Florida, Georgia and Michigan. This one is the reference he wished those contractors had.
How IRC span tables get onto this site
1. Read from the published code, not a screenshot
Span tables come from IRC 2021 as printed in the Seattle Residential Code PDFs: Chapter 5 for floor joists and deck joists, beams and posts, Chapter 6 for headers, and Chapter 8 for rafters and ceiling joists. Deck footing sizes come from AWC DCA 6-2015. Where Seattle amends a table, the struck original IRC wording is used and the amendment is ignored, so the tables match the model code.
2. Entered from the PDF, then checked against it
Each species, grade, size and spacing cell is entered as printed, with the footnotes it carries, and any cell misprinted in the published code is flagged rather than copied silently, then validated for gaps and out-of-order values before it goes live. Footnotes that change an answer, like deflection limits and wet-service use, stay attached to the result.
3. Rounded up, never interpolated
Inputs that fall between table values snap up to the next listed value. Nothing is interpolated. When a span is longer than the table allows, the tool says outside table rather than inventing a number.
Rounding policy, code editions and the source PDFs are listed on the methodology page. Found a cell that does not match the code book? Report it and it gets checked against the PDF.
What these construction calculators do, and what they leave alone
Who the calculators are built for
- Span lookups for floor joists, rafters, ceiling joists, deck joists, deck beams and headers
- Quantities: concrete, shingles, tile, drywall, board feet
- Layout: stair stringers, roof pitch, baluster spacing
- Homeowners, carpenters, deck builders and concrete crews, on a phone, on site
What the calculators are not built for
- Cost or price estimating. No material prices, no labor rates.
- Structural design. Beams, loads and connections beyond the printed tables need a licensed engineer.
- Step-by-step building instructions. The tools give numbers and the code section behind them, not a how-to.
- Local amendments. Your county may override the IRC. Check with your building department before you cut.
Questions about MyBuildingCalculators
Who runs MyBuildingCalculators.com?
Syed Zulqarnain builds and maintains the site, including the span-table data layer and the calculators themselves. He is a web builder who has spent six and a half years working with remodeling and construction contractors, not an engineer. The site has no other staff; questions and error reports go through the contact page and are answered by him.
Is the author a licensed structural engineer?
No. Zulqarnain is a site builder and data curator. The authority on this site is the published code, not the person entering it: every structural result names the code table it came from so you can verify it yourself. Anything that needs judgment beyond a printed table, like an unusual load or a span past the table's limit, is a job for a licensed engineer.
Where do the span numbers come from?
From IRC 2021 Chapters 5, 6 and 8, read from the Seattle Residential Code PDFs, plus AWC DCA 6-2015 for deck footing sizes. The methodology page lists every table, its page and how it was checked.
Which code edition do the calculators use?
IRC 2021 for every span table, including deck joists, beams and posts, with AWC DCA 6-2015 used only for deck footing sizes. Your inspector may enforce a different edition; how each source is used is explained on the methodology page.
Why does a result say the span is outside the table?
Because the code table stops there, and the tool reports that instead of extrapolating. What to do next is covered on the methodology page.
Do the calculators interpolate between table values?
No. An input between two listed values snaps up to the next value in the table. A worked example is on the methodology page.
Can I use a result from this site for a permit application?
Use it to check your numbers, not as the permit document. Plan reviewers work from the code edition and amendments your jurisdiction has adopted, and many require a stamped drawing for anything structural. Print the result with its assumptions and the table citation, then confirm it with your building department before you build.
Are the calculators free, and do I need an account?
Yes, free, and no. There is no signup, no email gate and no paid tier. Every tool runs in the browser, results print on one page with the inputs listed underneath, and the tools work on a phone on site.
Does the site estimate costs?
No. The calculators handle geometry, quantities and code-table lookups only: how much concrete, how many shingle bundles, how far a joist can span. Material prices and labor rates vary by region and month, so they are left out on purpose. Take the quantity to your supplier for a price.
I found a value that does not match the code book. What should I do?
Report it through the contact page with the tool name, the inputs you used and the table you checked against. The cell is compared to the source PDF and corrected if it is wrong. How cells are checked is explained on the methodology page.