Voltage Divider Calculator
Calculate the output voltage of a resistive divider and its loading effects.
About Voltage Divider Calculator
The ideal divider ratio only holds with no load. Any load appears in parallel with R2 and pulls the output down, which is why divider resistances must be low compared with the load impedance. A divider feeding a low-impedance load needs either much lower resistor values or a buffer amplifier, and the output impedance figure tells you which.
Formula
Voltage Divider
V_out = V_in × R2 ÷ (R1 + R2); loaded output uses R2 in parallel with the load
- output impedance
- R1 in parallel with R2, the Thévenin resistance seen by the load
Worked example
With the default values below, Voltage Divider Calculator returns Output Voltage of 3.8245. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Input voltageminimum 0 V
- 12 V
- Upper resistor R1minimum 0.01 ohm
- 10,000 ohm
- Lower resistor R2minimum 0.01 ohm
- 4,700 ohm
- Load resistance across the outputminimum 1 ohm
- 1,000,000 ohm
Results
- Output Voltage
- 3.8245 V
- Output With No Load
- 3.8367 V
- Current Through the Divider
- 0.000816 A
- Power Dissipated in the Divider
- 0.00980 W
- Output Impedance
- 3,197.28 ohm
Step by step
- 1Values used
- 2Voltage Divider
- 3Output Voltage= 3.8245 V
- 4Output With No Load= 3.8367 V
- 5Current Through the Divider= 0.000816 A
- 6Power Dissipated in the Divider= 0.00980 W
- 7Output Impedance= 3,197.28 ohm
Assumptions and limits
- The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax or compounding frequency into account.
- Figures are rounded for display to 6 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is Voltage Divider calculated?
V_out = V_in × R2 ÷ (R1 + R2); loaded output uses R2 in parallel with the load The ideal divider ratio only holds with no load. Any load appears in parallel with R2 and pulls the output down, which is why divider resistances must be low compared with the load impedance.
Why does Voltage Divider matter?
A divider feeding a low-impedance load needs either much lower resistor values or a buffer amplifier, and the output impedance figure tells you which.
What values do I need to enter?
This calculator takes 4 inputs: Input voltage, Upper resistor R1, Lower resistor R2, Load resistance across the output. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.