LED resistor calculator

LED Series Resistor Calculator

Compute the line resistor, current, power and recommended wattage. Compare with nearest E-series resistor.

Mode

Supply voltage (Vs)

LED forward voltage (Vf, per LED)

LED/string current (If)

LEDs per string (N)

Series resistor R

Parallel strings (S)

Invalid input. Check that Vs > N·Vf and values are > 0 for the selected mode.

Precision:

R (ideal)

N max (LEDs in series)

Current (single string)

If (ideal)

Voltage across resistor Vr

Resistor power (single string)

Total current (all strings)

Total resistor power (all strings)

Suggested resistor wattage (per string)

Nearest resistor series

R (nearest standard)

Current (rounded)

Resistor power (rounded, single)

Total current (rounded)

Total resistor power (rounded)

Error vs target/ideal

R = (Vs − N·Vf) / If, If = (Vs − N·Vf) / R, N_max = ⌊(Vs − If·R)/Vf⌋, P = I²·R.