Linear Regulator Efficiency Calculator Formula

Understand the math behind the linear regulator efficiency calculator. Each variable explained with a worked example.

Use the Linear Regulator Efficiency Calculator

Formulas Used

Efficiency

efficiency_pct = (v_out / v_in) * 100

Power Wasted

power_wasted_w = (v_in - v_out) * load_current_a

Power Delivered

power_delivered_w = v_out * load_current_a

Variables

VariableDescriptionDefault
v_inInput Voltage(V)12
v_outOutput Voltage(V)5
load_current_aLoad Current(A)1

How It Works

Linear Regulator Efficiency

Formula

Efficiency = V_out / V_in x 100%

Linear regulators are simple and low-noise but waste power as heat. Efficiency depends only on the voltage ratio, not on current. A 12V-to-5V linear regulator is only 42% efficient.

Worked Example

12 V input, 5 V output, 1 A load.

v_in = 12v_out = 5load_current_a = 1
  1. 01Efficiency = 5 / 12 x 100 = 41.7%
  2. 02Power delivered = 5 x 1 = 5 W
  3. 03Power wasted = (12 - 5) x 1 = 7 W

Ready to run the numbers?

Open Linear Regulator Efficiency Calculator