Circuit Calculator (Ohm's Law)
Ohm's law, resistor series/parallel, voltage dividers, RC time constants and LED resistor calculations for electronics work.
Fill in exactly two values; the other two are calculated.
How to use
- Choose a tab: Ohm's law, resistor combinations, voltage divider, RC time constant, or LED resistor.
- For Ohm's law, fill in exactly two of V, I, R and P and the other two are solved.
- For resistors, add or remove values and switch the unit between Ω, kΩ and MΩ.
- For an LED, you get the required resistance plus the next E12 standard value and the power the resistor dissipates.
Notes
All calculations use ideal-component DC formulas. Component tolerances, wiring resistance and temperature effects are not modeled. The LED resistor is rounded up to the next E12 value so the LED is never overdriven by a too-small resistor; in a real circuit, also leave headroom in the resistor's power rating.
FAQ
- Does it handle AC circuits or impedance?
- No. This tool covers DC resistive circuits only; reactance of coils and capacitors is not handled (the RC tab computes DC charging time only).
- What happens if I fill in three Ohm's law values?
- An error is shown, because the solver needs exactly two known values. Clear one field to continue.