Voltage Divider: 5V to 3.3V for Microcontrollers
Use a voltage divider with R1=10kΩ and R2=20kΩ to step a 5V logic signal down to approximately 3.3V.
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How to use this tool
- Enter input voltage (vin), r1 (top resistor) and r2 (bottom resistor) in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your output voltage (vout) and the full breakdown beneath it.
Level-shift a 5V logic signal down to 3.3V using a simple two-resistor voltage divider.
Frequently asked questions
- Why does the output voltage change when I connect a load?
- A load in parallel with R2 reduces the effective resistance, dropping Vout. For accurate division, the load resistance should be much larger than R2 (≥10×).
- How do I choose R1 and R2 for a target Vout?
- Rearrange: R1/R2 = (Vin − Vout)/Vout. Pick a convenient R2, then calculate R1.