Can I use a voltage divider as a power supply?

It is not recommended. The output voltage changes with the load current, so use a voltage regulator or a DC-DC converter for power.

Voltage Divider Calculator | Find E24 Resistor Pairs for a Target Voltage

Enter Vin and the target Vout to search for E24 resistor pairs.

Input voltage Vin

Target output voltage Vout

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E24 resistor pairs

Rank	R1 (upper)	R2 (lower)	Vout	Error (V / %)	Current	Rating

Do not use it as a power supply

A voltage divider is not suited to powering things. When the load current rises, Vout (the output voltage) drops, so use a voltage regulator to power microcontrollers and sensors.

Always check the ADC input limit

An ADC (analog-to-digital converter, the circuit that reads a voltage as a number) has a maximum input voltage. Feeding a 5 V signal straight into a 3.3 V device such as a Pico or ESP32 will damage it. Make sure the divided voltage stays below the limit.

A few kΩ to a few tens of kΩ is a good range

Very large resistors (a few hundred kΩ or more) are more affected by noise and the characteristics of the ADC input. Very small resistors draw more current.

What is a voltage divider? | Lowering a voltage with two resistors

A voltage divider is a basic circuit that connects two resistors in series to lower a supply voltage by a fixed ratio. As in the diagram above, the upper resistor R1 and the lower resistor R2 share Vin (the input voltage), and Vout (the output voltage) is taken from the point between R1 and R2, which is the voltage across R2 measured from GND (the 0 V reference). It is used for things like turning 5 V into 3.3 V, scaling sensor signals, and making reference voltages for microcontrollers.

The voltage divider formula: Vout = Vin × R2 / (R1 + R2)

The output voltage is Vout = Vin × R2 / (R1 + R2). R1 is the upper resistor (on the Vin side) and R2 is the lower resistor (on the GND side). For example, with Vin = 5 V, R1 = 5.1 kΩ, and R2 = 10 kΩ, Vout = 5 × 10 / (5.1 + 10) ≈ 3.31 V. The larger R2's share, the higher the output voltage.

How to use this tool | Find resistors and check Vout

Find resistors: Enter Vin and the Vout you need to list R1 and R2 pairs from the E24 series (standard resistor values you can buy), smallest error first.
Check Vout: Enter the R1 and R2 you have to work out the actual Vout. Add a load resistance RL to see how much the voltage drops when a load is connected.

Voltage divider FAQ

What resistors divide 5 V down to 3.3 V?

In the E24 series, R1 = 5.1 kΩ and R2 = 10 kΩ is a common choice, giving a Vout of about 3.31 V. The Find resistors tab calculates other candidates for you.

What is the voltage divider formula?

Vout = Vin × R2 / (R1 + R2). R1 is the upper resistor (on the Vin side) and R2 is the lower resistor (on the GND side).

Can I power a microcontroller from a voltage divider?

It is not recommended. When load current flows, Vout drops, so use a voltage regulator or a DC-DC converter for power. A voltage divider is meant for signals and reference voltages.

Should voltage divider resistors be large or small?

A few kΩ to a few tens of kΩ is a good starting point. Values that are too small draw more current and heat up, and values that are too large are more affected by noise and the ADC (analog-to-digital converter) input. This tool shows the balance with current and power warnings.

What is the E24 series, and why use these values?

The E24 series is a standard set of resistor values with 24 steps per decade: 10, 11, 12, and so on up to 91. Resistors are sold in these values, so candidates from the E24 series are combinations you can actually buy.