Trussly show formula feature: every calculator displays its formula and sources so you can check the math. Code-based calculators cite the 2021 IRC, IPC, or IFGC section they use. Part of Trussly, a $29.99 iOS construction calculator app with 85 calculators by Creayo LLC.

Every calculator shows its math

You shouldn't trust a calculator that won't show its work. Tap "Show Formula" on any Trussly calculator and you'll see the equation, the variables, and where the numbers come from: the code table, the manufacturer data sheet, or the industry publication.

The math, not a black box

The concrete slab calculator doesn't just say "4.2 cubic yards." It shows you the formula: length x width x depth / 27, plus the 10% over-order. You can check it with a pencil and explain it to a client.

This is how construction math should work. Transparent. Verifiable.

Code references built in

The wire size calculator explains which ampacity column applies to NM cable. The stair calculator cites IRC R311.7.5. The drain slope calculator cites IRC P3005.3. The gas pipe calculator names the IFGC table and row.

You'll see the specific code section next to the formula. Not buried in a help page. Right there, next to the math.

Every formula, visible

This applies to every calculator in the app. Concrete, framing, roofing, electrical, plumbing, HVAC, paint, tile, landscape, general. No hidden logic. No proprietary algorithms. Standard trade formulas, implemented correctly, shown openly.

If you find a formula you disagree with, you'll know exactly what it's doing and can decide for yourself.

Related features

  • Code References -- IRC, IPC, and IFGC citations on code-based calculators.
  • PDF Export -- export inputs and results as a printable worksheet.

Read more: How to Size Wire for a Circuit (NEC 310.16)

Get Trussly

Check the math yourself. Every formula, every code reference.