Ohm’s law and power
Solve any pair of voltage, current, resistance and power; check temperature derating.
Development preview. Check the assumptions below before relying on a result. Calculations run in your browser.
How it calculates
Model: V = IR; P = VI = I²R; allowed power = rating × clamp((Tzero − Ta)/(Tzero − Tknee), 0, 1)
Assumptions
- RP mode returns positive voltage/current.
- SMD size uses illustrative nominal ratings and 2× power headroom; actual part, board, voltage and pulse ratings govern.
Worked example
These are the calculator's default inputs. Change any input above to recalculate.
Inputs
- Known quantities
- vr
- Voltage
- 12 V
- Current
- 0.01 A
- Resistance
- 1000 Ω
- Power
- 0.1 W
- Rated power at knee
- 0.25 W
- Ambient temperature
- 25 °C
- Derating knee
- 70 °C
- Zero-power temperature
- 155 °C
Results
- Current
- 0.012 A
- Dissipation
- 0.144 W
- Voltage
- 12 V
- Resistance
- 1000 Ω
- Derated rating
- 0.25 W
- Rating utilisation
- 57.6 %
- Illustrative SMD starting size
- 1210