Fourteen free, browser-only calculators for electricians, contractors, and homeowners. Every tool runs entirely in your browser – nothing is sent to a server, no signup required, and no ads inside the calculator. Each tool links to the relevant code reference so you can verify the result yourself.
Electrical Code Calculators
- NEC Wire Size Calculator – Size copper or aluminum conductors by ampacity and voltage drop using NEC Table 310.16 and Table 310.12.
- Voltage Drop Calculator – Verify drop is inside the NEC 210.19(A) targets: 3% on branch circuits, 5% total feeder plus branch.
- Electrical Load Calculator (NEC 220) – Size a residential service using the NEC 220 standard method. Returns total VA, amps, and the next standard service size.
- Conduit Fill Calculator – Check EMT, IMC, RMC, and PVC Schedule 40/80 fill against NEC Chapter 9 Table 1 limits (40% for 3+ conductors).
- Box Fill Calculator (NEC 314.16) – Sum conductor, device, clamp, and EGC allowances and compare to the listed box volume.
- Motor FLA & Branch Circuit Calculator – Pull FLA from NEC Tables 430.247-250, apply the 125% branch-circuit factor per NEC 430.22.
- Grounding Conductor Sizer – Size the GEC (NEC Table 250.66) or EGC (NEC Table 250.122). Copper and aluminum.
Construction Estimating Tools
- Concrete Volume Calculator – Cubic yards and 80 lb bag count for slabs, footings, and round columns. Includes configurable waste allowance.
- Drywall, Mud & Tape Estimator – Sheet count, mud weight, tape footage, and screw count per room for 4×8, 4×10, and 4×12 sheets.
- Roofing Material Estimator – Roof squares, shingle bundles, underlayment rolls, and ridge cap linear feet from footprint plus pitch.
- Construction Markup Calculator – Convert margin to markup (and back), add overhead and profit, and see the full bid breakdown.
- Construction Unit Converter – Length, area, volume, lumber board feet, and AWG to mm2. All conversions auto-update as you type.
- Stair Stringer Calculator – Rise, run, stringer length, and stair count to IRC R311.7 limits. Flags non-conforming combinations.
- Solar Panel Payback Calculator – Simple payback period, lifetime production, and lifetime savings for a residential PV system.
Looking for state-specific NEC code information? See the Calculators Hub for per-state voltage drop and conduit fill pages, or visit the NEC Code Lookup Hub for article-by-article quick reference.
