Free Professional Calculators

Free voltage drop calculator for electricians. Calculate voltage drop, wire size, and max distance per NEC 210.19(A) guidelines.

Determine the correct wire size and AWG for your electrical project based on NEC Table 310.16 ampacity ratings and rules.

Calculate maximum conduit fill capacity per NEC Chapter 9. Easy tool for finding how many wires fit in EMT, PVC, and Rigid conduits.

Calculate electrical box fill volume to meet NEC 314.16 requirements. Prevent overcrowding and ensure safe wiring installations.

Work out an HVAC nameplate's minimum circuit ampacity under NEC 440.33, or read what a conductor you already have can carry. Free, with a printable Table 310.16 chart.

Size a breaker or fuse to NEC 240.6(A) — and only to NEC 240.6(A). General branch circuits round up to a minimum; HVAC circuits round down from a 175% maximum.

Size a dwelling service by the NEC 220.82 optional method — and see what the same house calculates under the 2026 code, where the article moved and two of the numbers changed.

The whole of NEC Table 250.122 — all 19 rows to 6000 A, copper and aluminum — with the 250.122(B) math for circuits whose conductors you already enlarged.

Calculate superheat and subcooling for R-410A, R-32, R-454B and R-22 — with the bubble-and-dew P-T chart the A2L refrigerants need, and a diagnosis that reads both numbers together.

Size ductwork from CFM with Darcy-Weisbach and Colebrook, see the roughness the answer used, and get the ACCA Manual D velocity and friction-rate verdict on top of the number.

Work out what a higher SEER2 system actually saves per year, convert SEER to SEER2 with the AHRI factor for your equipment class, and get the break-even year most calculators leave out.

Decode the nominal tonnage of an air conditioner or heat pump from its model number. Handles the published codes that the divide-by-12 shortcut gets wrong.

Free markup vs margin calculator for electrical contractors. Understand your profit margins and set the right prices for jobs.

Price your own electrical work. Build a burdened labor rate, add materials and overhead, and print a branded estimate free — no signup, no email.