Ohms Law Calculator

Enter any two known values and press "Calculate" to solve for the others. For example, a 100 watt light bulb operating on 120 volts AC will have 144 ohms of resistance and will draw 0.833 Amps. Enter 100 in the Watts field and 120 in the Voltage field and press Calculate to find the resistance and current. Fields should be reset to 0 before each new calculation.

Voltage (E) = Current (I) * Resistance (R)
Power (watts) = Current Squared (I^2) * Resistance (R)
Power = I*E = E^2 / R

  • Volts (E)
  • Amps (I)
  • Ohms (R)
  • Power (Watts)
  

Conversion Calculator

Distance / Length

  • Meters
  • Millimeters
  • Inches
  • Feet
  • Yards
  • Miles
  • Kilometers
  • Centimeters
  

Area

  • Square
    Meters
  • Square
    Millimeters
  • Square
    Inches
  • Square
    Feet
  • Square
    Yards
  • Square
    Miles
  • Square
    Kilometers
  

Volume U.S.

  • Liters
  • Fluid Ounces
  • Cubic Inches
  • Quarts
  • Gallons
  • Cubic Feet
  • Cubic Yards
  • Cubic Meters
  

Weights

  • Kilograms
  • Ounces
  • Pounds
  • English Tons
  • Metric Tons
  

Temperature

  • °C
  • °F
  

Pipe-Flow Calculator

  • Parameter
  • Symbol
  • Value
  • Length (m)
  • L
  • Kinematic viscosity (m²/s)
  • v
  • Equivalent sand roughness (m)
  • ks
  • Minor loss coefficient
  • K
  • Calculate or specify friction factor?
  •  
  • Friction factor
  • λ
  • Diameter (m)
  • D
  • Head loss (m)
  • h
  • Quantity of flow (m³/s)
  • Q

(Note that many engineers use f for friction factor, with λ being equivalent to either f or 4f. The value here is 4 times the skin-friction coefficient.)