Voltage Divider: 9V Battery to ~4.5V
Use equal resistors in a voltage divider to produce roughly 4.5V from a 9V battery.
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.
Tap the midpoint voltage of a 9V battery supply using a simple equal-value resistor 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.