Free calculators for the trades
Fast, no-clutter tools for electrical, HVAC, and plumbing sizing — built to load instantly on a phone on site, not slow you down.
Advertisement
Tools
Electrical
Wire Size Calculator
Enter load, distance, and voltage — get the smallest NEC-compliant wire gauge that meets your voltage-drop target.
Voltage Drop Calculator
Check the voltage drop for a given wire gauge, run length, and load — with a pass/fail against NEC-recommended limits.
Conduit Fill Calculator
Check how many conductors of a given size fit in EMT or PVC conduit, per NEC Chapter 9 fill rules.
Ampacity Calculator
Get the real, adjusted ampacity for a wire after ambient temperature and conductor-bundling derating.
Transformer Sizing Calculator
Enter load current, voltage, and phase — get the recommended standard transformer kVA size.
Generator Sizing Calculator
Enter running load and largest motor's starting surge — get the recommended standard generator size.
Electrical Service & Panel Load Calculator
NEC 220.82 optional method — enter square footage and appliance loads to get the recommended service size.
HVAC
BTU Calculator
Enter room size, climate, and occupancy — get the recommended BTU rating for a window or portable AC.
HVAC Load Calculator
Whole-house sizing estimate — square footage, climate, and insulation to recommended central system tonnage.
Mini-Split Sizing Calculator
Enter zone size, climate, and occupancy — get the recommended ductless mini-split head size.
Heat Pump Sizing Calculator
Recommended heat pump tonnage, plus balance-point guidance for cold-climate backup heat.
Duct Sizing Calculator
Enter CFM and duct location — get the recommended round duct diameter at the correct design velocity.
SEER Savings Calculator
Compare your current system's SEER rating to a replacement's — estimate annual electricity savings.
Refrigerant Charge Calculator
Enter nameplate base charge and line set length — get the total refrigerant charge needed.
Plumbing
Water Heater Size Calculator
Enter household size and bathroom count — get the recommended tank size in gallons.
Septic Tank Size Calculator
Enter bedroom count for a common baseline tank size — always verify against local code.
Water Pipe & PEX Sizing Calculator
Enter flow rate and line type — get the minimum recommended pipe diameter.
Well Pump Sizing Calculator
Enter required GPM and total dynamic head — get the recommended pump horsepower.
Sump Pump Sizing Calculator
Time your basin's fill rate — get the recommended pump horsepower.
These calculators provide reference-grade estimates based on published code tables and industry rule-of- thumb guidance (see each tool's disclaimer for its specific sources). They are not a substitute for a licensed electrician, HVAC technician, or plumber, or for the current edition of the relevant code.
Guides
NEC Wire Size ChartCopper and aluminum ampacity by AWG, in one lookup table.
BTU vs Tonnage ExplainedWhy 12,000 BTU equals 1 ton, and how to convert between them.
Tank vs Tankless Water HeaterDifferent sizing logic, cost, and capacity trade-offs compared.
When to DIY vs Call a Licensed ElectricianA practical line between safe DIY work and hiring a pro.
Advertisement