Free Tools
Free Tools for Trade Contractors
NEC-accurate electrical and HVAC calculators with no login, no email, and no ads. Built for electricians and HVAC technicians in the field.
Electrical Calculators
Every calculation cites the specific NEC table and section number. Show-the-math toggles explain the formula in plain English.
Wire Size Calculator
Find the correct wire gauge per NEC 310.16 with temperature derating, bundling adjustment, and 110.14(C) terminal temp enforcement.
Voltage Drop Calculator
Calculate voltage drop percentage for any wire run. Includes reverse-solve for minimum wire size to meet NEC recommendations.
Conduit Fill Calculator
Check NEC Chapter 9 conduit fill compliance for any combination of conductors. Supports EMT, IMC, RMC, PVC, and ENT.
Box Fill Calculator
Calculate junction box fill per NEC 314.16 with conductors, devices, clamps, EGCs, and terminal blocks.
Conduit Bending Calculator
Calculate marks for offsets, saddles, stubs, back-to-back 90s, and kick-90s with interactive SVG diagrams.
EV Charger Installation Calculator
Size wire, breaker, and panel capacity for Level 2 EV charger installs per NEC 625. Includes GFCI requirements and parts list.
MCA & MOCP Breaker Calculator
Enter the nameplate MCA and MOCP and get the wire size, breaker, ground, and voltage drop per NEC Article 440.
Electrical Load Calculator
NEC 220.82 service sizing and the 220.87 check: can this panel handle an EV charger or heat pump?
NEC 2026 Changes
Every verified change from NEC 2023, with unverified reports clearly separated.
NEC Adoption by State
The NEC edition in force in your state, with effective dates and NEC 2026 status. Updated monthly.
HVAC Calculators
Load sizing and refrigerant diagnostics with climate-zone data and pressure-temperature interpolation.
BTU / HVAC Load Calculator
Calculate cooling and heating load by climate zone, insulation, windows, and duct location. Whole-house or room-by-room with tonnage sizing.
Superheat & Subcooling Calculator
Check charge level with PT interpolation for 10 refrigerants including R-454B and R-32. Four-quadrant diagnostic decision tree.
EPA Refrigerant Leak Rate Calculator
Annualizing and rolling average methods, 10/20/30 percent thresholds, and repair deadlines under 40 CFR 84.106, effective January 1, 2026.
A2L Charge Limit Calculator
Maximum R-454B and R-32 charge by room area per UL 60335-2-40 and ASHRAE 15.2, or minimum room area for a given charge.
A2L Line Set Calculator
Line set sizing by tonnage and length plus a REUSE, FLUSH, or REPLACE verdict for reusing an R-410A set with R-454B or R-32.
Serial Number Lookup
Decode the manufacture date from an HVAC serial number for 50+ brands, with refrigerant era and warranty context.
Tonnage From Model Number
Decode nominal tonnage, BTU/h, and SEER and refrigerant hints from any AC or heat pump model number.
Reference Charts
Quick-lookup tables straight from the code: ampacity, conduit and box fill, grounding, derating, breaker sizes, and refrigerant properties. Every value cites its NEC table or standard.
Wire Ampacity Chart (310.16)
Copper and aluminum ampacities at 60, 75, and 90°C with the terminal-temperature and small-conductor rules.
Conduit Fill Chart (THHN in EMT)
Maximum THHN conductors per EMT trade size at the NEC 40% fill limit, #14 to 500 kcmil.
Box Fill Volume Chart (314.16)
Cubic inches per conductor and standard box volumes, with the device, clamp, and ground counting rules.
Ground Wire Size Chart (250.122)
Equipment grounding conductor size by breaker rating, with the 250.122(B) upsizing rule.
Ampacity Derating Factors (310.15)
Ambient temperature correction and conductor bundling adjustment factor tables.
Standard Breaker Sizes (240.6)
Every standard breaker and fuse rating 15A to 6000A, with the next-standard-size rule.
A2L Refrigerant Properties
GWP, safety class, and LFL for R-454B, R-32, R-410A, and the refrigerants of the A2L transition.
BTU Per Square Foot Chart
Cooling and heating BTU per square foot by climate zone, plus the tons-to-BTU conversion.
Business Tools
The money side of the trade: price jobs and convert markup to margin without the math.
Service Pricing Calculator
Calculate your true hourly rate based on income goals, overhead, taxes, and billable hours. Includes trade-specific benchmarks.
Markup vs Margin Calculator
Convert between markup and margin instantly. See both percentages side by side with trade-specific benchmarks for contractors.
Frequently Asked Questions
Are these tools really free?
Yes. Every tool is completely free: no login, no email gate, no ads. We build these tools because they help trade contractors do better work, and we think that earns trust. Accuracy and usefulness are the whole point; the site supports itself.
How accurate are the electrical calculators?
All electrical calculators reference the National Electrical Code (NEC) 2023 edition with specific table and section citations. Values are cross-referenced against published manufacturer data from Southwire, Greenlee, and Klein. If you spot an error, contact us. Accuracy matters.
Do I need to create an account to use these tools?
No. Every tool works instantly in your browser with zero signup. You can bookmark results or use the share button to generate a link with your inputs pre-filled.
Pick a calculator and get to work.
Wire sizing, conduit bends, BTU loads, pricing math: every tool cites its source so you can check the numbers yourself. No login, no email, ever.