Voltage Divider Calculator
Calculate output voltage, current, and output power for a two-resistor divider.
Check Voltage Divider Calculator
Voltage divider updated. Unloaded output 8.25 volts. Loaded output 7.7193 volts.
Reusable output
Copy the divider result before checking loading, tolerance, and resistor power.
Voltage divider result: Vin=12 V, R1=1,000 ohms, R2=2,200 ohms. Unloaded output: 8.25 V. Loaded output with 1.000e+4 ohms load: 7.7193 V. Divider current: unloaded 0.0038 A, loaded 0.0043 A. Tolerance band: +/-0.4125 V at 5%. Power check: R1=0.0183 W, R2=0.0271 W, selected rating=0.25 W, margin=9.2301x. Use the loaded output for ADC inputs, sensor dividers, and any circuit where the next stage is not high impedance.
Formula result
Check before you use it
What the numbers show
The answer shows what fraction of the supply appears at the output node and how much divider current the chosen resistor pair draws.
Use voltage divider calculator for ADC input scaling, sensor reference checks, bias-node setup, battery monitor ratios, and homework divider problems.
A load connected to the output node can pull the voltage lower than the ideal divider result.
Copy-ready formula handoff
Use this after solving the live calculator result, then paste the answer into a lab note, homework check, or engineering review.
Vout = Vs * R2 / (R1 + R2), Rbottom = R2 || Rload, Vloaded = Vs * Rbottom / (R1 + Rbottom)
- Supply voltage: Input voltage feeding the two-resistor chain.
- Top resistor: Resistor from the supply rail to the output node.
- Bottom resistor: Resistor from the output node to the reference or ground node.
- Output voltage: Ideal unloaded voltage measured across R2.
- The output node is treated as unloaded or connected to a much higher input resistance than R2.
- Resistors are ideal, the source is stable, and lead or contact resistance is ignored.
- Swapping R1 and R2; Vout is measured across the bottom resistor in this divider setup.
- Ignoring the load connected to Vout, which can place another resistance in parallel with R2.
Voltage Divider Calculator result: [paste the solved value from the calculator above]. Formula used: Vout = Vs * R2 / (R1 + R2), Rbottom = R2 || Rload, Vloaded = Vs * Rbottom / (R1 + Rbottom) Inputs checked: Supply voltage, Top resistor, Bottom resistor, Output voltage. Assumptions: The output node is treated as unloaded or connected to a much higher input resistance than R2. Resistors are ideal, the source is stable, and lead or contact resistance is ignored. Worked example: 12 V divider with R1 = 1 kohm, R2 = 2.2 kohm, and a 10 kohm load. Unloaded output is 12 * 2200 / 3200 = 8.25 V. The load makes the effective bottom resistance 2200 || 10000 = 1803.28 ohms, so loaded output is about 7.72 V. Loaded current is about 4.28 mA; compare each resistor power with the selected rating and keep margin for heat and tolerance. Next check: Swapping R1 and R2; Vout is measured across the bottom resistor in this divider setup.
Equation context
Built for ADC input scaling, sensor reference checks, bias-node setup, battery monitor ratios, and homework divider problems. This page pairs the live calculator with the governing formula, variable glossary, and a worked example so the result is easier to trust and reuse.
Quick entry points
Use the calculator to verify arithmetic after you set up the formula yourself.
Change one input at a time to see which variable is driving the result.
Review the formula notes before using the answer in a lab or design check.
Variables to track
Input voltage feeding the two-resistor chain. Unit: V.
Resistor from the supply rail to the output node. Unit: ohms.
Resistor from the output node to the reference or ground node. Unit: ohms.
Ideal unloaded voltage measured across R2. Unit: V.
Input or load resistance connected from the output node to ground. Unit: ohms.
Formula method and unit assumptions
Formula and example
Worked example
12 V divider with R1 = 1 kohm, R2 = 2.2 kohm, and a 10 kohm load
- 1Unloaded output is 12 * 2200 / 3200 = 8.25 V.
- 2The load makes the effective bottom resistance 2200 || 10000 = 1803.28 ohms, so loaded output is about 7.72 V.
- 3Loaded current is about 4.28 mA; compare each resistor power with the selected rating and keep margin for heat and tolerance.
The 0.53 V loading drop is why ADC inputs, sensor nodes, and reference dividers should be checked with the next-stage input resistance included.
Assumptions
Common mistakes
Related formula checks
Equation context and next checks
Formula and variable setup for Voltage Divider Calculator
Calculate output voltage, current, and output power for a two-resistor divider. The page is designed to help you move from the known values to the correct formula without rebuilding the derivation every time.
For voltage divider calculator, the safest workflow is to confirm the unit system first, then map each symbol to the physical quantity in your problem statement before solving.
- Vs: Supply voltage (V) - Input voltage feeding the two-resistor chain.
- R1: Top resistor (ohms) - Resistor from the supply rail to the output node.
- R2: Bottom resistor (ohms) - Resistor from the output node to the reference or ground node.
- Vout: Output voltage (V) - Ideal unloaded voltage measured across R2.
- Rload: Load resistance (ohms) - Input or load resistance connected from the output node to ground.
How to read the result
The answer shows what fraction of the supply appears at the output node and how much divider current the chosen resistor pair draws.
This tool is especially useful for ADC input scaling, sensor reference checks, bias-node setup, battery monitor ratios, and homework divider problems. The output becomes more trustworthy when you compare nearby cases instead of relying on one single run.
- Output voltage
- Divider current
- Output power estimate
Assumptions and limits
The calculator applies the standard textbook relation for this topic, which makes it a strong first-pass answer but not always a full real-world model.
Before you use the result in a lab, design review, or report, check whether the simplified assumptions still match the physical system you care about.
- The output node is treated as unloaded or connected to a much higher input resistance than R2.
- Resistors are ideal, the source is stable, and lead or contact resistance is ignored.
- Divider current and resistor power are derived from the same simple two-resistor model.
- A real load can change the effective bottom resistance and pull Vout away from the ideal result.
Quick glossary
Input voltage feeding the two-resistor chain.
Resistor from the supply rail to the output node.
Resistor from the output node to the reference or ground node.
A simplified physics model that omits secondary effects so the first-order relationship is easier to inspect.
Formula checks before using the result
Formula questions
Checks before using the result
When should I use the voltage divider calculator?
Use voltage divider calculator for ADC input scaling, sensor reference checks, bias-node setup, battery monitor ratios, and homework divider problems, especially when the governing formula is already known and the main need is a fast, transparent calculation.
What is the main thing the voltage divider calculator tells me?
The answer shows what fraction of the supply appears at the output node and how much divider current the chosen resistor pair draws.
What can make the voltage divider calculator answer inaccurate?
The answer is exact for the formula and assumptions on the page, but it can drift when the real system violates those assumptions. Common limits include The output node is treated as unloaded or connected to a much higher input resistance than R2. Resistors are ideal, the source is stable, and lead or contact resistance is ignored. Divider current and resistor power are derived from the same simple two-resistor model. A real load can change the effective bottom resistance and pull Vout away from the ideal result.
Formula references and related examples
Formula Basis