Resistor Calculator
Voltage Divider Calculator
Calculate R1 and R2 for any resistor voltage divider. Results snap to standard E24 resistor values, showing the actual output voltage and power consumption.
Common Presets
Quick-fill common voltage divider scenarios.
Enter Values
Vin and Vout are required. Load current is optional — helps size the resistors correctly.
Volts — source voltage
Volts — must be less than Vin
milliamps (mA)
—
Actual Vout
—
Power
—
Divider I
—
Circuit Diagram
Voltage Divider Formula:
Vout = Vin × R2 / (R1 + R2)
Design Rule:
Divider current ≈ 10× load current for stable Vout
R_total = Vin / I_divider
R2 = R_total × (Vout / Vin) · R1 = R_total − R2
Notes:
• Use E24 standard values for closest match
• Higher resistance = less power waste but more load sensitivity
• For precise regulation, use a voltage regulator (LM317, LDO)
Vout = Vin × R2 / (R1 + R2)
Design Rule:
Divider current ≈ 10× load current for stable Vout
R_total = Vin / I_divider
R2 = R_total × (Vout / Vin) · R1 = R_total − R2
Notes:
• Use E24 standard values for closest match
• Higher resistance = less power waste but more load sensitivity
• For precise regulation, use a voltage regulator (LM317, LDO)