# Voltage Regulation Calculator

URL: https://speedycalculator.com/calculators/physics/voltage-regulation/
Last updated: 2026-10-30

> The voltage regulation calculator finds the percentage voltage regulation of a transformer, generator or power supply from its no-load and full-load output voltages.

## Inputs

- No-load voltage V_NL (V, kV, mV)
- Full-load voltage V_FL (V, kV, mV)

## Results

- Voltage regulation
- Voltage drop

## Formula

```
Regulation (%) = (V_NL − V_FL) / V_FL × 100
```

## Explanation

Good power sources keep their voltage steady as load changes. Voltage regulation measures how much the output sags from no load to full load – a few percent for a good transformer, near zero for an electronic regulator.

### How to use the Voltage Regulation Calculator

- **No-load voltage V_NL**
- **Full-load voltage V_FL**

Results update as you type, every field has its own unit menu, and everything is calculated in your browser.

### How it works

Enter the output voltage with no load and at full load.

### Inputs explained

FieldWhat to enterNo-load voltage V_NLUnits: V, kV, mVFull-load voltage V_FLUnits: V, kV, mV

### What each result means

- **Voltage regulation** = ([No-load voltage V_NL] - [Full-load voltage V_FL])÷[Full-load voltage V_FL]×100
- **Voltage drop** = [No-load voltage V_NL] - [Full-load voltage V_FL]

### Example values

How the main result changes when **No-load voltage V_NL** changes and everything else stays at the example values above:

No-load voltage V_NL (V)Voltage regulation (%)120-47.8261180-21.73912404.347830030.434836056.5217480108.6957

## Worked example

Inputs — No-load voltage V_NL: 240 V; Full-load voltage V_FL: 230 V.

Results — **Voltage regulation = 4.3478 %**; Voltage drop = 10 V.

## Key terms

- **Full load**: The rated maximum load.

## FAQ

**What is good regulation?**
2–5% for distribution transformers; under 1% for regulated supplies.

**Why does voltage drop under load?**
Winding resistance and leakage reactance.

**Can regulation be negative?**
Yes, with capacitive loads.

**Lower or higher is better?**
Lower – the voltage changes less.


## Sources

- [OpenStax – University Physics Volume 2](https://openstax.org/details/books/university-physics-volume-2)
- [The Engineering ToolBox](https://www.engineeringtoolbox.com/)