Ohm's law equations
Voltage, current, resistance, and power describe one resistive operating point.
V = I × RP = V × I = I² × R = V² / Rwhere:
- V
- Voltage[V]
- I
- Current[A]
- R
- Resistance[Ω]
- P
- Electrical power[W]
These relationships apply directly to DC and ideal resistive loads.
Ohm's Law Formula Wheel
This formula wheel is a visual reference for the relationships between power (P), current (I), voltage (V), and resistance (R). It represents the same algebra used by the calculator above. Find the quantity you want to calculate in the center, then choose the equation in that section that contains your two known values.
How to use the Ohm's Law Calculator
Voltage, current, resistance, and power are shown together. Select any two quantities as known inputs and enter their values in the units shown; the other two values update immediately in the result panel.
- Select two known quantities from V, I, R, and P.
- Enter both known values.
- Read the two calculated values in the result panel.
- Check all four quantities against component ratings.
Calculation method and validation
The equations and symbol definitions above show the complete calculation basis. Inputs are checked before calculation so zero, negative, incompatible, or physically impossible combinations are flagged instead of silently producing a misleading result.
How to interpret the result
Use the main result as a starting value and read every supporting metric. DC or purely resistive steady-state circuit Both entered values describe the same operating point A passing or recommended result means the entered mathematical conditions are satisfied; it does not certify the complete installation or a particular product combination.
- DC or purely resistive steady-state circuit
- Both entered values describe the same operating point
Selection limits and next checks
Preliminary engineering estimate only. Verify the final design against the current applicable standard, local rules, manufacturer data, and project conditions. Compare the output with the current applicable standard, local rules, exact VIOX product datasheet, environmental conditions, protection coordination, and the engineer's project requirements before procurement or installation.
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Assumptions
- DC or purely resistive steady-state circuit
- Both entered values describe the same operating point
Important Warnings
- Preliminary engineering estimate only. Verify the final design against the current applicable standard, local rules, manufacturer data, and project conditions.