About FieldsCalc

FieldsCalc is built and maintained independently — we're not a contractor, an equipment manufacturer, or a trade association. The site exists because the free field-calculation tools already online tend to check only one requirement at a time — ampacity or voltage drop, but rarely both — and are often slow enough that using one on a phone, on site, is genuinely annoying. We build tools that check every relevant requirement together and load instantly.

What we build

Free, no-signup calculators for the trades — electrical (wire sizing, voltage drop, conduit fill, ampacity, transformer and generator sizing, service load), HVAC (BTU, whole-house load, mini-split, heat pump, duct sizing, SEER savings, refrigerant charge), and plumbing (water heater, septic tank, pipe sizing, well pump, sump pump). Every calculator is built on published code reference tables and documented, checkable formulas — see the Guides section for the reasoning and the math behind each tool, not just the answer. Every technical claim in the guides is checked against the code section or published rule-of-thumb source it cites, not written from memory.

What we're not

We're not a licensed electrician, HVAC technician, or plumber, and nothing on this site is a substitute for one. These tools give you a fast, reference-grade estimate to work from — for anything beyond a simple, low-risk job, or anywhere your local code has amendments to the base code, confirm with a licensed professional in the relevant trade. See when to DIY vs call a licensed electrician for more on where that line sits. Because we're not tied to a specific contractor network or supplier, the calculators and reference data are the same regardless of who you end up hiring.

How this site makes money

Through display advertising and an affiliate relationship with Angi (see our Affiliate Disclosure) — every tool on this site remains free to use, with no signup or paywall.