Electrical
Resistor Divider Calculator
Calculate unloaded resistor divider output voltage from input voltage in V and upper and lower resistances in kΩ, with a 12 V worked example.
How it works
Vout = Vin × R2 / (R1 + R2)
For Vin = 12 V, R1 = 10 kΩ and R2 = 4.7 kΩ, Vout = 12 × 4.7 / (10 + 4.7) = 3.84 V (rounded).
R1 connects Vin to the output node; R2 connects the output node to ground. Both resistances use the same unit, so their ratio is unchanged.
FAQ
Where is the output voltage measured?
Measure from the junction of R1 and R2 to the grounded end of R2.
Does this include the attached load?
No. A load in parallel with R2 changes the effective lower resistance and therefore the output voltage.
Can I enter zero resistance?
Either resistor may be zero, but they cannot both be zero. Negative resistance is rejected. Negative input voltage is allowed.