8 min read
Voltage Drop Formula & Examples
A practical guide to voltage drop formulas, one-way cable length, temperature-adjusted resistance, and checking a result against wire ampacity.
Read the guide →Electrical planning center
Electrical Calculators and Planning Guides
Estimate electrical load, check preliminary wire ampacity, understand voltage drop, and calculate three-phase current in one organized toolbox.
A practical sequence
Move from load to conductor review
01
Estimate load
Organize lighting, appliances, HVAC, and connected versus demand load.
Open tool →02Calculate current
Use kW, kVA, voltage, and power factor for three-phase equipment.
Open tool →03Screen ampacity
Compare current with preliminary conductor ampacity assumptions.
Open tool →04Check voltage drop
Review cable length, resistance, temperature, and circuit type.
Open tool →Free tools
Electrical calculators
Each tool shows its assumptions so you can carry the planning basis into a quote, load schedule, or professional review.
Electrical tool
Voltage Drop Calculator
Estimate voltage loss from current, cable length, conductor resistance, temperature, and circuit type.
Open calculatorElectrical tool
Wire Size / Ampacity Calculator
Screen conductor ampacity with load current, continuous-load planning, temperature, and current-carrying conductors.
Open calculatorElectrical tool
Electrical Load Calculator
Organize connected load, preliminary demand load, appliances, HVAC, lighting, and estimated service current.
Open calculatorElectrical tool
3-Phase Load Calculator
Calculate balanced or phase-by-phase kW, kVA, line current, phase current, and current imbalance.
Open calculatorField Notes
Electrical planning guides
8 min read
Wire Size vs Voltage Drop
Ampacity and voltage drop answer different design questions. This guide shows how to check both without treating a calculator result as final code approval.
Read the guide →8 min read
3-Phase Current: kW, kVA & Amps
A clear guide to line current, phase current, apparent power, power factor, Wye versus Delta, and the limits of balanced-load formulas.
Read the guide →8 min read
Electrical Load: Connected vs Demand
Understand connected load, demand load, heating and cooling diversity, continuous-load planning, and why a calculator cannot approve service size.
Read the guide →Before you design
Electrical calculator FAQs
Which electrical calculator should I use first?
Start with Electrical Load when you are estimating the total demand for a dwelling or project. Use the 3-Phase Load Calculator for three-phase equipment, then check wire ampacity and voltage drop separately.
Can these calculators approve a wire, breaker, or service size?
No. They are preliminary planning tools. Final electrical design must consider the adopted code, equipment nameplates, installation method, ampacity, protection, voltage drop, grounding, utility requirements, and qualified professional review.
Are the electrical calculators free to use?
Yes. The StructoCalc electrical calculators are available without an account and support Metric and US Customary inputs where applicable.