EMBEDDED TOOL
Voltage Divider Calculator
Calculate output voltage from two resistors, or the R2 needed to hit a target voltage.
Output voltage
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Divider current
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About this tool
Calculate the output of a two-resistor voltage divider (Vout = Vin × R2 ÷ (R1 + R2)), or flip it around to find the R2 value needed to hit a target output voltage for a chosen R1 — handy for sensor reference voltages, level-shifting, or feeding a lower voltage into an ADC.
Frequently asked questions
- Which resistor is R1 and which is R2?
- R1 is the resistor between Vin and the output tap, and R2 is the resistor between the output tap and ground — the output is measured across R2.
- Why does the divider current matter?
- It tells you how much current is continuously drawn through the divider (I = Vin ÷ (R1+R2)), which matters for battery-powered designs — a low-resistance divider wastes more power, while a very high-resistance divider becomes sensitive to loading from whatever it's connected to.
- Does this account for the load connected to the output?
- No — this is the unloaded (open-circuit) divider equation. If you connect something with a comparable or lower impedance to the output tap, it will pull Vout lower than this calculation shows.