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Potentiometer Output Calculator

Work out potentiometer output instantly with clear inputs, formula shown and shareable results.

About Potentiometer Output Calculator

An unloaded potentiometer is a linear divider: output equals supply times the fractional position. Adding a load puts resistance in parallel with the lower leg, pulling the output down. The error is worst at mid-travel, where the wiper's source impedance peaks at a quarter of the total resistance.

Formula

Loaded divider

Vout = V x (Rlower || Rload) / ((Rlower || Rload) + Rupper); source Z = Rlower x Rupper / Rtotal

Worked example

With the default values below, Potentiometer Output Calculator returns Output voltage of 1.6692. Change any input above and every figure here is recalculated in your browser.

Inputs used

Supply voltage
5 V
Total pot resistance
10,000 Ω
Wiper position
35 %
Load resistance on the wiper
47,000 Ω

Results

Output voltage
1.6692 V
Unloaded output voltage
1.7500 V
Loading error
4.617% %
Source impedance at the wiper
2,275.00 Ω

Step by step

  1. 1Values used
  2. 2Loaded divider
  3. 3Output voltage= 1.6692 V
  4. 4Unloaded output voltage= 1.7500 V
  5. 5Loading error= 4.617 %
  6. 6Source impedance at the wiper= 2,275.00 Ω

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax or compounding frequency into account.
  • Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Electrical results are planning estimates only. Verify against the applicable wiring rules (IEC 60364, BS 7671, NEC or local code) and have all installation work designed and checked by a qualified electrician.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Electrical results are planning estimates only. Verify against the applicable wiring rules (IEC 60364, BS 7671, NEC or local code) and have all installation work designed and checked by a qualified electrician.

Frequently Asked Questions

How large should the load be?

At least 100 times the pot resistance to keep loading error under about 0.25%. Otherwise buffer the wiper with an op-amp follower.

Where is the loading error largest?

Near the middle of travel, because that is where the wiper's source impedance is highest.

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