Voltage Divider Calculator
Enter the input voltage and the two resistors to get the output voltage, current and power, with a live circuit diagram that updates as you type. Formula: Vout = Vin × R2 ÷ (R1 + R2).
होमैये: Vout = Vin × R2 ÷ (R1 + R2). सापेट डालें, नॆटडाइट्राप सादे सादा आसानी सादी सादे यॆसीने पासा पॆच्ता है एह युजैल दालें। सापेट लाइन सादे सादी दालें। पाता है एदा दालें।
Formula: Vout = Vin × R2 ÷ (R1 + R2). Values dalo, live circuit diagram apne aap update hota rahega.
How the voltage divider works
Two resistors in series divide the input voltage in proportion to their resistance. The output is taken at the point between them:
- R1 sits between the input voltage and the output node.
- R2 sits between the output node and ground.
- The same current flows through both, so each resistor takes a share of the voltage proportional to its resistance.
Worked examples
| Input | R1 | R2 | Output | Use case |
|---|---|---|---|---|
| 5 V | 5 kΩ | 5 kΩ | 2.5 V | Half voltage, balanced divider |
| 5 V | 10 kΩ | 20 kΩ | 3.33 V | 5 V logic to 3.3 V input (Arduino to ESP32/Raspberry Pi) |
| 12 V | 14 kΩ | 10 kΩ | 5 V | 12 V battery to 5 V sensor reading |
| 9 V | 1 kΩ | 1 kΩ | 4.5 V | Battery midpoint reference |
| 14.4 V | 4.7 kΩ | 1 kΩ | 2.55 V | Car battery voltage into a microcontroller ADC |
Real uses of a voltage divider
- Logic level shifting — drop a 5 V signal to 3.3 V so an ESP32, Raspberry Pi or 3.3 V sensor input is not overdriven.
- Battery voltage sensing — scale a battery voltage down to the range a microcontroller ADC can read.
- Reference voltage — a fixed fraction of a supply as a comparison level.
- Volume / sensor trimming — potentiometers are simply adjustable voltage dividers.
Important: a divider is for signals and references only. The moment a load draws real current from the output, the voltage sags — see the next section. To power something, use a regulator or buck converter instead.
Why the output drops when you connect a load
A load connected to the output acts like a third resistor in parallel with R2. The combined resistance is smaller than R2, so the divider ratio shifts and Vout falls. Rule of thumb: keep the load resistance at least 10× larger than R2, or buffer the output with an op-amp or emitter follower.
FAQ
What is the voltage divider formula?
Vout = Vin × R2 ÷ (R1 + R2). With 5 V in and 5 kΩ + 5 kΩ: Vout = 5 × 5000 ÷ 10000 = 2.5 V.
How do I convert 5 V to 3.3 V with resistors?
You need a ratio of 0.66. Use R1 = 10 kΩ, R2 = 20 kΩ: Vout = 5 × 20000 ÷ 30000 = 3.33 V. Fine for a 5 V logic output feeding a 3.3 V high-impedance input. It cannot power a device.
Can I power a device from a divider?
No. Any load current pulls the output voltage down. Use a regulator (78XX, LDO, buck module) for powering.
How much current flows?
I = Vin ÷ (R1 + R2). 5 V across 10 kΩ total = 0.5 mA. Smaller resistors give a stiffer divider but waste more current.
What power rating do I need?
P = I² × R for each resistor. The 5 V / 10 kΩ example dissipates 1.25 mW per resistor — any resistor handles that. Check power for low-ohm or high-voltage dividers.
Does it work for AC?
Yes — resistive dividers divide AC and DC alike at any instant. At high frequencies stray capacitance matters.
About this tool
Built by Sayan Roy Chowdhury, the engineer behind Byte Sherlock in Barrackpore, West Bengal. Voltage dividers come up daily in repair work — battery sense lines, level-shifted signals, dead-board tracing. If your board is beyond a calculator, that is our job: see laptop repair or mobile repair.
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