Voltage Divider
Vout = Vin × R2 / (R1 + R2)
Quick answer
This calculator solves Vout = Vin × R2 / (R1 + R2) for Output Voltage. With Input Voltage 26.4 V, R1 (upper) 10 kΩ, R2 (lower) 22 kΩ, the result is 18.15 V. It solves in 4 directions, so you can enter the values you have and get the one you need.
Calculator
Formula
Description
A voltage divider is a simple two-resistor circuit that produces an output voltage that is a fraction of the input voltage. It is one of the most common subcircuits in electronics, used for biasing transistors, creating reference voltages, interfacing sensors, and scaling signals down to levels safe for ADC inputs on microcontrollers. The output voltage depends only on the ratio of R2 to the total resistance, not their absolute values, though lower values waste more current and higher values are more susceptible to noise.
Variables
- Vin — Input voltage in volts (V)
- R1 — Upper resistor connected to Vin (Ω)
- R2 — Lower resistor connected to ground (Ω)
- Vout — Output voltage taken across R2 (V)
Practical Notes
This formula assumes no load on the output. Any load in parallel with R2 reduces the effective lower resistance and drops Vout. For high-impedance loads like op-amp inputs or MOSFET gates this effect is negligible, but for low-impedance loads you must account for the parallel combination of R2 and the load.
Symbols and units
| Symbol | Meaning | Default unit | Accepted units |
|---|---|---|---|
| Vout | Output Voltage | V | pV, nV, µV, mV, V, kV |
| Vin | Input Voltage | V | pV, nV, µV, mV, V, kV |
| R1 | R1 (upper) | kΩ | mΩ, Ω, kΩ, MΩ |
| R2 | R2 (lower) | kΩ | mΩ, Ω, kΩ, MΩ |
Step by step
- 1. What you know: Input Voltage 26.4 V, R1 (upper) 10 kΩ, R2 (lower) 22 kΩ
- 2. The relation: Vout = Vin × R2 / (R1 + R2)
- 3. Substitute: Vin = 26.4 V, R1 = 10 kΩ, R2 = 22 kΩ
- 4. Result: Output Voltage = 18.15 V
Related quantities from the same inputs
- P = V² / R = 69.7 mW
- I = V / R = 2.64 mA
Worked examples
Minimum range
Given: Input Voltage 0.726 V, R1 (upper) 100 Ω, R2 (lower) 0.22 kΩ
Result: Output Voltage = 0.4991 V
Low range
Given: Input Voltage 7.26 V, R1 (upper) 1 kΩ, R2 (lower) 2.2 kΩ
Result: Output Voltage = 4.991 V
Typical
Given: Input Voltage 26.4 V, R1 (upper) 10 kΩ, R2 (lower) 22 kΩ
Result: Output Voltage = 18.15 V
High range
Given: Input Voltage 0.506 kV, R1 (upper) 100 kΩ, R2 (lower) 0.22 MΩ
Result: Output Voltage = 0.3479 kV
Maximum range
Given: Input Voltage 5.06 kV, R1 (upper) 1 MΩ, R2 (lower) 2.2 MΩ
Result: Output Voltage = 3.479 kV
Solving for each variable
Solve for Output Voltage
Input Voltage 0.726 V, R1 (upper) 100 Ω, R2 (lower) 0.22 kΩ → 0.4991 V
Solve for Input Voltage
Output Voltage 0.33 V, R1 (upper) 100 Ω, R2 (lower) 0.22 kΩ → 0.48 V
Solve for R1 (upper)
Output Voltage 0.33 V, Input Voltage 0.726 V, R2 (lower) 0.22 kΩ → 0.264 kΩ
Solve for R2 (lower)
Output Voltage 0.33 V, Input Voltage 0.726 V, R1 (upper) 100 Ω → 83.33 Ω
How Output Voltage changes with Input Voltage
| Input Voltage (input) | Output Voltage (result) |
|---|---|
| 5.81 V | 3.994 V |
| 14.53 V | 9.986 V |
| 29.05 V | 19.97 V |
| 43.58 V | 29.96 V |
| 58.1 V | 39.94 V |
| 87.15 V | 59.92 V |
| 116.2 V | 79.89 V |
| 0.2324 kV | 0.1598 kV |
| 0.4067 kV | 0.2796 kV |
| 0.581 kV | 0.3994 kV |
The same result in other units
| Unit | Value |
|---|---|
| mV | 18150 |
| V | 18.15 |
| kV | 0.01815 |
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<p><a href="https://vbatpower.com/formulas/voltage-divider/">Voltage Divider</a> Calculator by vbatpower.com</p>Frequently asked questions
How do you calculate Voltage Divider?
Use Vout = Vin × R2 / (R1 + R2). With Input Voltage 26.4 V, R1 (upper) 10 kΩ, R2 (lower) 22 kΩ, Output Voltage works out to 18.15 V.
What is the formula for Voltage Divider?
The formula is Vout = Vin × R2 / (R1 + R2). A voltage divider is a simple two-resistor circuit that produces an output voltage that is a fraction of the input voltage.
How do you find Input Voltage when you know the other values?
Rearrange for Input Voltage: with Output Voltage 0.33 V, R1 (upper) 100 Ω, R2 (lower) 0.22 kΩ, Input Voltage is 0.48 V.
How do you find R1 (upper) when you know the other values?
Rearrange for R1 (upper): with Output Voltage 0.33 V, Input Voltage 0.726 V, R2 (lower) 0.22 kΩ, R1 (upper) is 0.264 kΩ.
What units does Voltage Divider use?
Output Voltage is shown in mV, V, kV. Values are held in SI base units internally, so you can mix prefixes without converting by hand.
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