Electrical Calculators
Ohm's law, voltage drop, resistor codes, LED resistors, battery runtime and solar sizing — published constants, estimate framing.
About these electrical calculators
Almost everything in this category descends from one relationship: voltage equals current multiplied by resistance, and power equals voltage multiplied by current. The Ohm's Law Calculator solves that wheel from any two values; the Watts to Amps Converter is the same wheel read at a stated voltage, with the power-factor and three-phase terms shown rather than hidden; and the LED Resistor Calculator is the wheel applied to a single component, with the answer rounded up to the nearest standard E12 value because resistors are bought from a series, not made to order. Where a constant is needed it is a published one and it is printed on the page: copper's resistivity of 1.68 × 10⁻⁸ Ω·m and aluminium's 2.82 × 10⁻⁸ Ω·m in the voltage-drop table, the standard AWG cross-sections, and the full resistor colour table — digit, multiplier, tolerance and temperature coefficient — that the colour-code picker is built from.
The remaining tools are estimation tools and they say so. The Voltage Drop Calculator works out how much voltage a cable run loses at a stated current using those resistivity constants, and presents the answer per gauge so a run can be compared across sizes — but a drop percentage is a sizing estimate, not a ruling on whether an installation complies with the wiring code that governs it, and no page in this category issues one. The Battery Life Calculator divides capacity by load with an efficiency factor you set, because real discharge is never the laboratory figure. The Solar Panel Calculator sizes a panel array and battery bank from your daily load and your sun-hours, with the derate and depth-of-discharge assumptions exposed as inputs — change the assumption and the sizing changes with it, openly.
Two working habits apply across the category. First, every figure can be checked: formulas are printed in plain notation, worked examples show their substitutions, and any result can be reproduced with a hand calculator from the constants on the page. Second, the inputs that vary by place and tariff are always yours to enter — the Electricity Cost Calculator asks for your own rate per kilowatt-hour rather than consulting a table of tariffs that would differ by supplier and expire by season. And like everything on Kwikfig, all of it computes in your browser: circuit values, battery sizes and solar loads are never uploaded, stored or tracked.
Frequently asked questions
Are these calculators a substitute for electrical codes or an electrician?
No. They apply published formulas and constants to the values you enter, for planning and learning. Wiring regulations, breaker and cable ratings, and installation safety are governed by your local electrical code and the judgement of a qualified electrician, and where a page gives a sizing figure it is labelled an estimate for exactly that reason.
Which constants do the electrical calculators use?
Published ones, printed on the pages that use them: copper resistivity 1.68 × 10⁻⁸ Ω·m, aluminium 2.82 × 10⁻⁸ Ω·m, standard AWG cross-sectional areas in mm², the E12 resistor series, and the standard resistor colour table for digits, multipliers, tolerances and temperature coefficients.
Do these tools store my circuit or solar figures?
No. Every electrical calculator runs entirely in your browser. Voltages, loads, battery sizes and tariffs are calculated on your own device and are never sent to a server, stored or tracked — close the tab and they are gone.