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Electrical / Ohm's Law Calculator
OneFreePlace · Tool #151

Ohm's law that goes beyond four empty boxes.

Solve any V/I/R/P pair, analyze a complete series or parallel resistor network, or design a current-limiting resistor against real E-series values. See power dissipation, resistor-tolerance current ranges, thermal headroom and circuit cross-checks—all locally in your browser.

✓ All 6 V/I/R/P pairs✓ Series + parallel networks✓ E6–E96 resistor values✓ Tolerance analysis✓ Thermal margin
Ohm's Law Calculator
V · I · R · P · networks · resistor design
Calculation engine

Choose the electrical problem you actually have.

Two-known-value solverSelect exactly which two quantities are known. The other two are calculated live.
Electrical result
Calculating
—
calculated current
Enter valid circuit values.
Voltage V—across the analyzed element/network
Current I—through the analyzed element/network
Resistance R—equivalent resistance where applicable
Power P—electrical power dissipation
Conductance G—1 / R
Energy / design context—optional secondary analysis
Resistive modelOhm's law here assumes DC or a purely resistive AC element. Reactive impedance is outside this tool.

Formula audit

See which Ohm's-law and power relationships were used, with all values normalized to base SI units.

Circuit cross-check

Single-element results verify equivalent formulas. Network mode checks KVL/KCL-style sums and total power.

Network / standard-value breakdown

Network mode shows each resistor's voltage, current and power. Design mode compares nearby preferred resistor values.

Tolerance & thermal analysis

Design mode shows current and resistor power at tolerance extremes plus a planning-only resistor wattage floor.

Useful derived quantities

Model boundaries

Same-element / same-node ruleDo not combine voltage across an entire network with current through one unrelated branch when applying V = IR.
Fundamental
Pure resistance onlyInductors, capacitors and frequency-dependent loads require impedance/reactance analysis rather than a resistance-only model.
Scope
Not a mains-safety design toolComponent voltage ratings, insulation, fault energy, fusing, creepage, clearance and local electrical rules are outside this calculator.
Safety boundary
i
Resistor wattage is not just the calculated dissipation.Real components have temperature, pulse, voltage and mounting limits. The design lab's rating floor simply divides predicted dissipation by your chosen maximum utilization percentage; verify the actual resistor datasheet before building hardware.