Voltage Divider Calculator

Voltage Divider is evaluated from Input Voltage, Resistor R1 and Resistor R2. The calculation reports Output Voltage, Voltage Ratio and R2 for target Vout.

Results

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About the Voltage Divider Calculator

Voltage Divider is treated here as a quantitative relation between Input Voltage, Resistor R1, Resistor R2 and Target Vout and Output Voltage, Voltage Ratio, R2 for target Vout and Divider Current.

The calculator uses a multi formula configuration. Each reported value is read as a direct evaluation of the stored rules with the declared field formats and units.

Formula basis:
Vout = Vin x R2 / (R1 + R2)
R2 = Vout x R1 / (Vin - Vout)
I = Vin / (R1 + R2) (in amperes)

Interpret the outputs in the order shown by the result fields. Optional inputs affect only the outputs that depend on those variables.

Formula & How It Works

The calculation applies the following relations exactly as recorded in the metadata:

Vout = Vin x R2 / (R1 + R2)
R2 = Vout x R1 / (Vin - Vout)
I = Vin / (R1 + R2) (in amperes)

Each output field is produced by substituting the supplied inputs into the relevant relation and then applying the declared rounding or text format.

Worked Examples

Example 1: 5V to 3.3V Level Shift — Arduino to ESP32

Inputs

vin: 5 r1: 10000 r2: 20000

Output Voltage: 3.3333 V. Voltage Ratio: 0.6667. Divider Current: 0.1667 mA

With Input Voltage = 5, Resistor R1 = 10,000 and Resistor R2 = 20,000 as the stated inputs, the result is Output Voltage = 3.3333 V, Voltage Ratio = 0.6667 and Divider Current = 0.1667 mA. Each value corresponds to the declared output fields.

Example 2: Find R2 for 2.5V Reference

Inputs

vin: 5 r1: 10000 vout: 2.5

R2 for target Vout: 10,000 Ω

With Input Voltage = 5, Resistor R1 = 10,000 and Target Vout = 2.5 as the stated inputs, the result is R2 for target Vout = 10,000 Ω. Each value corresponds to the declared output fields.

Example 3: 12V Car Battery Monitor → 5V ADC

Inputs

vin: 12 r1: 33000 r2: 22000

Output Voltage: 4.8 V. Voltage Ratio: 0.4. Divider Current: 0.2182 mA

With Input Voltage = 12, Resistor R1 = 33,000 and Resistor R2 = 22,000 as the stated inputs, the result is Output Voltage = 4.8 V, Voltage Ratio = 0.4 and Divider Current = 0.2182 mA. Each value corresponds to the declared output fields.

Example 4: NTC Thermistor Temperature Sensor

Inputs

vin: 3.3 r1: 10000 r2: 10000

Output Voltage: 1.65 V. Voltage Ratio: 0.5. Divider Current: 0.165 mA

With Input Voltage = 3.3, Resistor R1 = 10,000 and Resistor R2 = 10,000 as the stated inputs, the result is Output Voltage = 1.65 V, Voltage Ratio = 0.5 and Divider Current = 0.165 mA. Each value corresponds to the declared output fields.

Common Use Cases

Scale 5V sensor output down to 3.3V for a microcontroller
Design a bias voltage network
Find R2 for a target output voltage