Voltage divider calculator
A divider is only accurate while the load draws far less current than the divider itself. This shows exactly how much it sags.
V
ohm
ohm
ohm
Output voltage, unloaded
6.000 00V
- Output voltage with the load
- 5.714 29 V
- Sag caused by the load
- 4.7619 %
- Quiescent current through the divider
- 0.0006 A
- Power wasted in the divider
- 0.0072
Show the working
- Input voltage = 12
- Top resistor R1 = 10 000
- Bottom resistor R2 = 10 000
- Load resistance = 100 000
- Output voltage, unloaded = 12 * 10 000 / (10 000 + 10 000) = 6
- Quiescent current through the divider = 12 / (10 000 + 10 000) = 0.0006
- r2_loaded = 10 000 * 100 000 / (10 000 + 100 000) = 9090.91
- Output voltage with the load = 12 * 9090.91 / (10 000 + 9090.91) = 5.714 29
- Sag caused by the load = 6 > 0 ? (6 - 5.714 29)/6*100 : 0 = 4.7619
- Power wasted in the divider = 12^2 / (10 000 + 10 000) = 0.0072
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
Scenarios & local history
Compare a saved scenario
Recent calculations
The formula
- Vout = Vin R2 / (R1 + R2)
- with a load, R2 becomes R2 in parallel with the load
A useful rule: keep the divider current at least ten times the load current if you want the unloaded formula to hold.