What this calculator actually models
Ohm's Law relates voltage, current and resistance with V = I × R. Once voltage and current are known, electrical power follows from P = V × I. Enter any two positive values and the calculator derives the other two.
How to use this calculator
Enter any two known positive values among volts, amps, ohms and watts.
Leave the other two fields empty.
Review all four calculated quantities and the input pair used.
Where people use it
- •Electronics and DC circuit checks
- •Sanity-checking equipment nameplate relationships
- •Electrical training and formula verification
Example: 12 V and 6 Ω
With 12 V across 6 Ω, current is 12 ÷ 6 = 2 A and power is 12 × 2 = 24 W.
Assumptions and limits
- •This ideal calculation treats resistance as purely resistive. AC impedance, phase angle, inrush current and nonlinear loads require additional information.
- •Do not use a simple Ohm’s Law result alone to select protective devices, conductor sizes or certify code compliance.
Frequently asked questions
What is Ohm's Law?+
The basic relationship is V = I × R, where V is volts, I is amps and R is ohms.
Why does the calculator ask for two values?+
Two independent positive quantities are enough to solve the remaining voltage/current/resistance/power relationships for a simple resistive circuit.
Does this calculate AC impedance?+
No. This page is an ideal resistive Ohm/Watt law calculator, not a full complex-impedance solver.
Semantic next steps
Continue the calculation
These links move to a different input, formula or project stage rather than a keyword variation of this page.
Reactance Calculator — Inductive XL, Capacitive XC & LC Resonance
Calculate inductive or capacitive reactance, reverse-solve frequency or component value, or find ideal LC resonant frequency with engineering-unit inputs and visible formulas.
OpenInternal Resistance Calculator — Battery Load Test, Two Points & Voltage Sag
Estimate a source or battery internal resistance from open-circuit and loaded voltage, from two load points, or run the internal-resistance model forward to check sag, loss and efficiency.
OpenWatts to Amps Calculator — DC, Single-Phase and Three-Phase
Convert watts to amps from power and voltage for DC, single-phase AC or balanced three-phase AC, with an explicit power-factor input for AC loads.
OpenSeries & Parallel Resistor Calculator — Equivalent Resistance
Calculate equivalent resistance for up to four resistors in series or parallel, with reciprocal working shown and an optional source voltage for total current.
OpenLED Resistor Calculator — E12/E24 Value, Color Code & Power
Calculate a simple DC LED current-limiting resistor, round upward to E12/E24, recalculate actual current and power, and show the selected resistor’s standard 4-band color code.
OpenBattery Runtime Calculator — Wh/Ah, Load, DoD & Efficiency
Estimate battery runtime from Wh or Ah capacity, voltage, load, usable depth of discharge and conversion efficiency, while keeping ideal and adjusted runtime separate.
OpenAmps to Watts Calculator — DC, Single-Phase & Three-Phase
Convert current in amps to real power in watts for DC, single-phase AC or balanced three-phase AC with explicit voltage and power-factor inputs.
OpenThree-Phase Power Calculator — kW, kVA, kVAR & Power Factor
Calculate balanced three-phase apparent, real and reactive power from line-to-line voltage, current and power factor, with phase angle shown for the simplified power triangle.
OpenMore in this calculator collection
Browse nearby calculators in the same topic cluster so related pages reinforce each other instead of sitting as isolated URLs.
Free publisher widget
Put this calculator on your website
Give readers the live calculator without rebuilding the math. Copy the responsive embed in one click, or customize width, height, border and corner radius before publishing. The branded MAXScanner attribution stays visible.
Calculator embed HTML
Paste this code into your page. Focus the code box to select it manually.
Keep the result connected to the real job
MAXScanner keeps the formula and assumptions beside the result so you can verify the number before using it in a drawing, estimate, specification, worksheet or document. Where a supplier, manufacturer, drawing or applicable standard owns a requirement, that source remains authoritative.