Engineering tools
Ohm's law, resistor color codes, voltage dividers, power and electrical energy calculators for engineering coursework and labs — with formulas and examples.
5 live tools1 in development
Ohm's Law Calculator
Solve V = IR instantly. Enter any two of voltage, current and resistance — get the third plus power dissipation. Supports k, M, m, µ and n prefixes.
Resistor Calculator
Decode 4-band and 5-band resistor color codes instantly — value, tolerance and range. Includes a color guide for lab work.
Voltage Divider Calculator
Calculate Vout for any resistor divider, or design one: find R2 for a target output voltage. Includes divider ratio and circuit current.
Power Calculator
Calculate electrical power from any two of voltage, current and resistance (P = VI). Instant watts with unit-prefix support for lab values.
Electrical Energy Calculator
Convert electrical power and time into energy: joules, kilowatt-hours and electricity cost. Perfect for lab reports and understanding power bills.
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Guides for engineering students
The Engineering Calculator Guide: Every Formula You Need in the Lab
Ohm's law, power, energy, voltage dividers and resistor codes — the complete set of calculations behind first-year circuits, with worked examples.
Aug 9, 2026 · 8 min read
How to Calculate Electrical Power: P = VI Explained
Power in watts from voltage, current and resistance — the three formulas, a worked example, and the resistor-rating mistake that starts fires (small ones).
Aug 5, 2026 · 4 min read
Resistor Color Codes Explained: How to Read Any Resistor
Digit bands, multiplier bands, tolerance bands — how to decode 4-band and 5-band resistors in seconds, plus the trick for reading them the right way round.
Aug 9, 2026 · 5 min read
Voltage Divider Explained: The Two-Resistor Circuit Behind Every Sensor
How Vout = Vin × R2/(R1+R2) works, when it breaks (loading), and how to design a divider for a target voltage — with worked examples.
Aug 9, 2026 · 5 min read
Engineering questions, answered
What is Ohm's law?
V = I × R — voltage equals current times resistance. Enter any two values in the Ohm's law calculator and it solves the third.
How do I read a resistor's value?
Color bands encode digits, a multiplier and tolerance. The resistor calculator decodes 4-band and 5-band codes instantly.