ohm's law calculator
Ohm's law ties voltage, current, resistance and power together by V = I × R and P = V × I. Fill in any two of the four fields — leave the other two blank — and the rest are solved for, shown in every unit.
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Formulas
These four — voltage V (volts), current I (amps), resistance R (ohms) and power P (watts) — are the corners of the “Ohm's law wheel”. Any two of them fix the other two, so there are six pairs you can start from; this calculator picks the right formula for whichever two you fill in.
Every value is converted through SI base units (volt, ampere, ohm, watt), so you can mix prefixes freely — e.g. 5 V across 220 Ω, or 1 kV at 1 mA. The answer is then expressed in every prefix of that quantity (µ, m, base, k, M, and GΩ) so you can read off whichever you need. Ohm's law applies to ohmic DC circuits; for AC, reactive or non-linear parts (diodes, motors) it's only an approximation.