⚡ Electronics Calculator

Calculate Ohm's law, LED resistor values, power consumption, and voltage dividers.

⚡ V💡 LED🎯 Ω

V = I × R · I = V / R · R = V / I · P = V × I

Voltage V
5 V
Current I
0.02 A
Resistance R
250 Ω
Power Consumption:
0.1 W

Frequently Asked Questions

Why does an LED need a resistor?

LEDs do not self-limit current. Without a resistor, excessive current will burn the LED. A series resistor keeps current at a safe level (typically 10–20 mA).

What are E24 standard resistor values?

The E24 series has 24 standard values between 10 and 100 Ω. Use the closest standard value (rounding up is safer) when the calculated value is not available.

What are voltage dividers used for?

Common uses include stepping down a 5V signal to 3.3V for a microcontroller, generating a reference voltage for an ADC, and monitoring battery voltage.