Voltage Divider Ratio Chart

Use this voltage divider ratio chart after the calculator result to document Vin, R1, R2, unloaded Vout, source current, and whether the connected input will load the divider.

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Quick reference table

A two-resistor divider gives Vout = Vin x R2 / (R1 + R2): 24 V to 10 V uses 14 kOhm and 10 kOhm, while 5 V to 3.3 V uses 5.1 kOhm and 10 kOhm. That calculator result is only a starting point: a meter input, PLC analog input, sensor input, or downstream circuit can sit in parallel with R2 and pull the output lower. Use this chart to choose the ratio, check divider current, and decide whether a buffer, different resistor values, or a real regulator is needed.

Common unloaded divider picks

Common unloaded divider picks
Use case	Vin	R1	R2	Unloaded Vout
24 V control signal to 10 V reference	24 V	14 kOhm	10 kOhm	10.0 V
24 V control signal to 5 V reference	24 V	38 kOhm	10 kOhm	5.0 V
12 V source to 5 V logic sense	12 V	14 kOhm	10 kOhm	5.0 V
5 V source to 3.3 V input	5 V	5.1 kOhm	10 kOhm	3.31 V
10 V reference to 2.5 V test point	10 V	30 kOhm	10 kOhm	2.5 V

Load check after the calculator result

Load check after the calculator result
Connected input compared with R2	Likely effect	Action before using the value
100x R2 or higher	Divider usually stays close to the unloaded result	Document the input resistance and meter check
10x R2	Output can shift enough to matter for analog work	Recalculate with the load in parallel with R2
Similar to R2	Output can be far below the expected ratio	Use lower resistor values, a buffer, or a different circuit
Unknown input impedance	The chart result is incomplete	Find the input specification or measure before relying on Vout

Formula basis

Vout = Vin x R2 / (R1 + R2). Divider current = Vin / (R1 + R2).

Vin is the input voltage across the complete divider.
R1 is the upper resistor from Vin to the output node.
R2 is the lower resistor from the output node to the reference side.
Vout is measured across R2 before any connected load changes the effective lower resistance.

Worked examples

Scale a 24 VDC signal for a 0 to 10 V inputWith R1 = 14 kOhm and R2 = 10 kOhm, the calculator result is 24 x 10 / 24 = 10 V and divider current is 1 mA. If the analog input is 100 kOhm, R2 becomes about 9.09 kOhm in parallel and Vout drops to about 9.45 V, so the load must be included.

Create a 3.3 V sense point from a 5 V board railWith R1 = 5.1 kOhm and R2 = 10 kOhm, Vout is about 3.31 V. The divider current is only about 0.33 mA, which is useful for sensing but not for powering a 3.3 V load.

Assumptions. Balanced load and line-to-line voltage assumptions behind this chart.

The ratio table is for simple two-resistor dividers used for sensing, references, and bench checks.
A connected input, meter, or module load changes the effective value of R2 and can change the calculator result.
Resistor tolerance, power dissipation, input protection, noise, and source limitations still need project-specific review.

Code and standard notes. Planning limits that should be checked before final equipment selection.

This chart is a circuit worksheet and does not replace component ratings, input specifications, or a regulated power supply design.

How to use this chart

1Choose the target outputStart with the voltage the receiving input actually expects, then pick a ratio that lands near that value from the available source voltage.

2Check divider currentUse Vin divided by total resistance to confirm the divider is not wasting too much current or becoming too weak for the input.

3Add the connected loadAfter the calculator result, compare the input resistance with R2 and recalculate if the load is close enough to disturb Vout.

Worksheet checklist. Record source basis, review gaps, and assumptions before using the chart result.

Record source and targetWrite the source voltage, desired output voltage, and receiving input type before selecting resistor values.
Calculate unloaded resultDocument R1, R2, Vout, divider current, and resistor power so the bench measurement has a clear baseline.
Document loaded resultAdd input impedance or measured load, then note whether the loaded Vout is still acceptable for the circuit.

Common mistakes to avoid. Review these before turning chart current into an equipment decision.

Treating the unloaded divider calculator result as final when the connected input is close enough to load R2.
Using very high resistor values on a noisy or high-impedance input without checking measurement stability.
Using a divider as a power source for a load whose current changes during operation.

Frequently asked questions

These answers explain how to use the chart without turning a quick reference into a final design decision.

Why does the load change a voltage divider result?

The load sits in parallel with R2, which lowers the effective lower resistance and changes the ratio used by the calculator.

Can a voltage divider power a device?

Usually no. A divider is normally for sensing or references. Use a regulator or power supply when the downstream device draws changing current.

What should I record after using the calculator?

Record Vin, R1, R2, unloaded Vout, divider current, the connected input impedance, and the loaded Vout check.