Potentiometer Calculator

About the Potentiometer Calculator

Potentiometers are among the most common electronic components, used in volume controls, sensor interfaces, calibration circuits, and anywhere a variable voltage or resistance is needed. Understanding how wiper position, load impedance, and taper type affect output voltage is crucial for proper circuit design. Small changes in loading can make a control feel wrong even when the nominal resistance value looks correct on paper.

This potentiometer calculator handles both voltage divider and rheostat configurations. Enter the total resistance, input voltage, wiper position, and optional load resistance to see the output voltage, current draw, power dissipation, and loading error. It supports linear and logarithmic (audio) taper calculations.

Whether you're designing an audio volume control, a sensor conditioning circuit, or simply need to set a trimmer pot, this calculator gives you the exact numbers. The comparison table shows how output changes across the full rotation range, and the loading effect analysis reveals when you need a buffer amplifier.

When This Page Helps

Use this calculator when a potentiometer has to behave like a predictable control point rather than a rough knob. It is useful for audio, sensor, and calibration circuits where load effects and taper shape change the actual output more than people expect. It also helps you decide when a simple divider is fine and when a buffer stage is the safer design choice.

How to Use the Inputs

1. Enter the potentiometer total resistance value (e.g., 10 kΩ).
2. Enter the input (supply) voltage applied across the pot.
3. Set the wiper position from 0% to 100% (or use the slider).
4. Select the taper type — linear (B) or logarithmic (A) for audio.
5. Optionally enter a load resistance to see loading effects.
6. Review output voltage, current, and power dissipation.
7. Check the sweep table for output at every 10% position.

Example Calculation

Tips & Best Practices

• Choose a pot value 10× smaller than the load for <5% loading error.
• Use a log taper (A) for volume controls and a linear taper (B) for everything else.
• Wire the unused terminal to the wiper as a safety measure — if the wiper loses contact, you get full voltage instead of an open circuit.
• For precision circuits, use multi-turn cermet trimmer pots.
• Add a small series resistor (100Ω) to limit current if the pot is accidentally shorted.
• Measure actual resistance with a multimeter — tolerance can be ±20% on cheap pots.

Potentiometer Taper Types Explained

Linear taper (Type B) pots produce a straight-line relationship between rotation and resistance. At 50% rotation, resistance is 50% of total. These are ideal for sensor circuits, calibration, and any application where resistance should change uniformly.

Logarithmic taper (Type A) pots follow a curve that approximates human perception. At 50% rotation, resistance might be only 10-15% of total. This matches how our ears perceive volume — a log pot feels linear to our hearing. Reverse-log (Type C) pots are the mirror image and are rarely used.

Loading Effects in Voltage Dividers

The most common mistake with potentiometers is ignoring load impedance. An ideal voltage divider (infinite load) gives Vout = Vin × position. But real loads create a parallel resistance that distorts the transfer curve, especially around the midpoint. With a load equal to the pot value, maximum error reaches 25%. With a load 10× the pot, error stays below 2.5%.

Practical Applications

Audio: Use 10-50 kΩ log taper for volume, 250 kΩ for guitar tone controls. Sensor conditioning: Use 10 kΩ linear for adjusting reference voltages. Motor control: Use wirewound rheostats rated for the motor current. LED dimming: A pot driving a transistor base or MOSFET gate provides smooth brightness control.

Frequently Asked Questions

• What is the difference between linear and logarithmic taper?

  Linear (B) taper changes resistance proportionally to rotation. Log (A) taper changes slowly at first then rapidly — matching human hearing perception for volume controls.

• How does load resistance affect output?

  A load in parallel with the lower half of the pot reduces effective resistance, pulling output voltage down. Use loads at least 10× the pot value to minimize this effect.

• What power rating do I need?

  Typical small pots handle 0.1-0.5W. Calculate power as V²/R and add a 50% safety margin. For higher power, use wirewound pots rated 1-5W.

• When should I use a rheostat configuration?

  Use rheostat (two-terminal) mode when you need variable resistance, like controlling motor speed or LED brightness. Connect the wiper to one end terminal.

• What causes noise in potentiometers?

  Wiper contact noise comes from dirty tracks, worn spots, and oxidation. Carbon composition pots are noisier than cermet or conductive plastic types.

• Why buffer the output?

  An op-amp voltage follower eliminates loading effects entirely, making the output equal to the ideal divider voltage regardless of downstream impedance. This is the right fix when the load is too low compared with the pot value.