Ohmbook

Ohmbook is an electrical circuit calculator for students, hobbyists and engineers. Pick a formula, choose what you want to find, enter the values you know, and Ohmbook solves it instantly and shows every step of the working. Whether you are checking homework, sizing a resistor at the workbench or revising for an exam, Ohmbook turns the formulas from your textbook into calculators you can actually use. 62 FORMULAS ACROSS 8 FIELDS • DC Circuits: Ohm's law, power, series and parallel resistance, voltage and current dividers, Kirchhoff's laws, Thévenin and Norton equivalents, superposition, maximum power transfer, Wheatstone bridge and delta–wye conversion • AC & Impedance: RMS values, angular frequency, capacitive and inductive reactance, series RLC impedance, phase angle, resonance, power factor and apparent power • Capacitors & Inductors: capacitance, stored energy, series and parallel networks, RC charging, and RC and RL time constants • Filters: RC and RL cutoff frequencies, quality factor, bandwidth and decibel gain • Electromagnetism: Coulomb's law, electric field, magnetic force, Faraday's law, magnetic flux, solenoids and transformers • Semiconductors & Op-Amps: diode equation, LED resistors, transistor gain, and inverting, non-inverting, summing and differential amplifiers • Power & Energy: energy use, efficiency, three-phase power and battery runtime • Signals & Digital: period and frequency, duty cycle and Nyquist rate SOLVE FOR ANY VARIABLE Every formula is an interactive calculator, not just a reference card. Choose the unknown and Ohmbook rearranges the equation for you. Need the current instead of the voltage? Tap once. SEE EVERY STEP Ohmbook doesn't just give you an answer. It shows the formula it used, converts your values to base units, substitutes them and solves, so you can follow the method and check your own working. LIVE CIRCUIT DIAGRAMS Many calculators include a schematic or graph that updates as you type, showing currents, voltages and component values right on the circuit. REAL-WORLD UNITS Tap µ, m, k or M instead of typing powers of ten. Results are shown in clear engineering notation, like 3.79 kΩ or 816 µA, with all related quantities shown alongside. PRACTICAL ANSWERS Calculating a resistor? Ohmbook suggests the nearest standard E24 value and shows the result you'd get with it, so you can go straight to a real part. BUILT FOR QUICK ACCESS • Search every formula by name or symbol • Star your favourites to find them in Saved • Jump back to recent formulas from History • Look up SI prefixes and units at a glance • Choose your own accent colour PRIVATE AND OFFLINE Ohmbook works entirely on your device. No account, no ads, no tracking and no internet connection needed, so it's ready in the lab, in class or at the workbench. Available for iPhone and iPad.