Electrical Fundamentals
Voltage Divider Calculator
The purpose of Voltage Divider is to turn source voltage, upper resistance, and lower resistance into output voltage. Keep the source condition with the saved result so later comparisons remain meaningful.
Set up the Voltage Divider case
Use measurements from one operating condition.
Understanding the equation
For this worksheet, the governing relationship is Vout = Vin × Rbottom ÷ (Rtop + Rbottom). Its variables correspond to Source voltage, Upper resistance, and Lower resistance.
The initial scenario returns 3.84 V. Re-enter field data before using the answer in a design or comparison.
Find the unloaded voltage-divider output. Keep Loaded Voltage Divider Calculator available for the companion calculation.
Sensitivity check
Change Source voltage from 12 V to 14.399999999999999 V with the rest of the inputs held constant. The comparison runs from 3.84 V to 4.60 V.
Keep both cases when the changed input represents genuine uncertainty.
Values this page needs
Keep source conditions with each voltage, current, resistance, or charge value. If operating conditions changed between readings, calculate separate cases.
At least one field has a positive lower bound because it appears in a denominator. A prefix error can move the result by several orders of magnitude.
- Source voltage
- Default example: 12 V. Enter source voltage in V.
- Upper resistance
- Default example: 10000 Ω. Enter upper resistance in Ω.
- Lower resistance
- Default example: 4700 Ω. Enter lower resistance in Ω.
Checks that catch bad inputs
An unlabeled assumption can make an otherwise correct result unusable.
Trace an unexpected result back through the raw entries first.
Interpreting the answer
The primary answer, Output voltage, describes only the entered scenario. Compare it with bench measurements and component ratings.
A result without its source conditions is difficult to compare or audit.
Practical limits
A connected load changes the lower branch resistance and therefore the output.
Additional checks may be needed for instrument loading, transient behavior, and component tolerance. Document which effects were checked elsewhere in the analysis.
Keep source conditions with each voltage, current, resistance, or charge value.
Before relying on the answer
Which assumptions matter most here?
The result follows the displayed variables. Check instrument loading, transient behavior, and component tolerance separately.
Why does the field result disagree with this page?
First confirm that the measurements match the equation. Then review lead and contact resistance, source impedance, and temperature drift.
What should remain fixed in an alternate case?
Keep unaffected entries fixed so the cause of the difference remains visible. Record conductor temperature and whether values are measured, nominal, or calculated.
What else is required before final selection?
No. Compare the value with a second case representing tolerance or temperature and apply relevant equipment and installation requirements.
When should I round output voltage?
Keep full precision while transferring output voltage; round only at the final reporting or selection step.
Which entries must stay above zero?
Use a measured positive value for Upper resistance and Lower resistance; zero cannot stand in for missing data.