Electrical & Technical DIY Calculators
Educational Ohm’s law, watts↔amps, voltage drop, wire/breaker sizing, load, battery, and LED resistor worksheets—learning estimates only, not a substitute for a licensed electrician, NEC, or local code.
Calculators
Professional tools with instant results
Ohm's Law Calculator
Solve Ohm’s law for voltage, current, resistance, or power from any valid pair of known values—clear DC/resistive relationships for DIY electronics.
Watts to Amps Calculator
Convert watts to amps for DC or single-phase AC, with optional power factor and three-phase mode—educational load estimates.
Amps to Watts Calculator
Convert amps to watts for DC or single-phase AC, with optional power factor and three-phase mode—mirror of the watts-to-amps worksheet.
Voltage Drop Calculator
Estimate one-way run voltage drop from amps, length, AWG, and copper/aluminum resistance tables—educational planning aid.
Wire Size Calculator
Estimate a minimum AWG from load amps, length, voltage, and a max drop % using simplified ampacity and resistance tables—with strong educational caveats.
Breaker Size Calculator
Estimate a standard breaker amp rating from load amps using a continuous-load ×1.25 rule of thumb—educational only, not code approval.
Electrical Load Calculator
Add up to four watt loads, convert to amps at your voltage, and apply an optional continuous factor for educational circuit planning.
Battery Runtime Calculator
Estimate how long a battery can run a watt load from amp-hours, voltage, depth of discharge, and efficiency—simple DC energy math.
Battery Capacity Calculator
Estimate the amp-hours you need for a watt load and target runtime, including depth of discharge and efficiency factors.
LED Resistor Calculator
Size a series resistor for one or more LEDs from supply voltage, forward voltage, and forward current—plus a preferred E24 value and power estimate.
Learn & Understand
In-depth guides and educational content
Ohm's Law Basics: Voltage, Current, Resistance, and Power
Learn the V = I·R relationships and when DIY Ohm’s law math stops being enough for real AC loads.
Wire Sizing Caveats: Ampacity, Drop, and Why Tables Lie to Beginners
Understand why educational AWG estimates differ from NEC designs—ampacity columns, temperature, terminations, and voltage drop.
Voltage Drop Basics for DIY Circuit Planning
See how length, current, and conductor resistance create voltage drop—and how percent drop relates to equipment performance.
Latest Articles
Expert insights and analysis
How Voltage Drop Worksheets Work
See how educational voltage-drop worksheets combine AWG resistance tables with one-way length and load current—and where real designs diverge.
Electrical DIY Safety: What These Calculators Are Not
Read how Free Calculators Hub frames electrical DIY math as learning tools—never a substitute for licensed electricians, NEC, or local permits.
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