Electrical Calculators (Free)

Electrical Calculator Toolbox — one place for the everyday electrical math

Need the numbers before you pull wire or quote a job? This electrical calculators page gives you fast answers for voltage drop, wire size/AWG, single-phase & three-phase power, and kW↔kVA↔kVAR conversions. Because speed matters in the field, every tool is lightweight, clear, and tuned for typical NEC workflows.

Start here of electrical calculators

• Voltage Drop Calculator — single/three-phase, percent drop and suggested wire size. → /voltage-drop-calculator
• 1-Phase / 3-Phase Power Calculator — P-V-I-PF math with kW/kVA/kVAR. → /single-three-phase-power-calculator
• Wire Size Calculator (AWG ↔ mm²) — pick a run, current, and drop target. → /wire-size-calculator
• kW ↔ kVA ↔ kVAR Converter — quick power triangle math. → /kw-kva-kvar-calculator
• PF (Power Factor) Calculator — find PF from kW and kVA, or solve for current. → /power-factor-calculator

Tip: If you work residential 120/240 V or commercial 277/480 V, these tools default to those values so you can move faster.

Why electricians use calculators instead of “head math”

On a long day it’s easy to miss a factor of 2L on single-phase, forget the √3 on three-phase, or mix up kW and kVA. Therefore, a reliable calculator prevents change orders, nuisance trips, and callbacks. In addition, it helps apprentices learn the pattern while keeping journeymen quick and consistent.

When should you use which electrical calculators?

• Sizing a branch circuit or feeder — start with Voltage Drop; if you’re near 3% at the branch or 5% total, bump the conductor.
• Figuring motor or EV charging load — use the 1ϕ/3ϕ Power Calculator with actual PF; as a result, your breaker and conductor choice matches real demand.
• Comparing copper vs aluminum — run the same current/length in the Wire Size Calculator; however, always check terminals and torque listings.
• Estimating generator/UPS size — convert with kW↔kVA↔kVAR and set a sensible PF.

Voltage drop: when is it critical?

• Long exterior runs: driveway lighting, detached garages, docks.
• Starting loads: well pumps, compressors, heat pumps, and EVSE—keep branch drop tighter than 3%.
• Low-voltage lighting & controls: even small absolute loss is a big percent at 12/24 V.
• Commercial three-phase: the geometry helps, nevertheless, check both feeder and branch because margins stack.

How this toolbox fits your learning path (skill tree)

Beginner → learn the P-V-I-PF triangle and try the 1ϕ/3ϕ power tool.
Intermediate → practice voltage drop and wire size decisions with a 3% / 5% target.
Advanced → layer on ampacity, derating, and OCPD coordination; then verify against your local code.

Extended reading about electrical calculators (internal links)

• Panel upgrades & breaker selection
• AFCI/GFCI protection basics → /afci-gfci-guide
• Copper vs Aluminum — wire size & ampacity → /wire-size-ampacity

References (outbound links)

• NEC informational notes on voltage drop (3% / 5%)
• Engineering Toolbox — conductor resistivity tables
• NEMA/ANSI wire and AWG references

Disclaimer: These calculators are for education and pre-design checks. Therefore, final selections must follow the NEC and local amendments, equipment listings, and the AHJ or project engineer. When in doubt, upsize and document your assumption.

FAQ