calc.engineer / PCB & Electronics / LED Resistor

LED Resistor v1.0.0

Calculates the current-limiting resistor for driving one or more LEDs in series from a DC supply. Computes the exact resistance from R = (Vsupply - n*Vf) / I, then selects the nearest E24 standard resistor value. Reports the actual current with the standard resistor, power dissipation, and voltage across the resistor. Supports series LED strings by specifying led_count. Validates that supply voltage exceeds total forward voltage. Chain from ohms_law for power budgeting or into trace_width for PCB layout.

← from ohms_law← from resistor_color_codefeeds trace_width →feeds ohms_law →
Supply voltage in volts (V). Must be positive.
LED forward voltage in volts (V). Defaults to 2.0V (typical red LED).
Desired LED current in milliamps (mA). Defaults to 20mA.
Number of LEDs in series. Defaults to 1.
Fill in the inputs and Compute to see the structured result.

From an agent (MCP) or the API

curl -X POST https://calc.engineer/api/led_resistor \
  -H "Content-Type: application/json" \
  -d '{"supply_voltage_v": …, "led_forward_v": …, "led_current_ma": …}'

MCP: connect to https://calc.engineer/mcp and call led_resistor.

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