# EUI Calculator (Energy Use Intensity)

URL: https://speedycalculator.com/calculators/everyday-life/eui/
Last updated: 2026-10-25

> The EUI calculator works out a building's energy use intensity – annual energy per square foot or square metre – and compares it with the ENERGY STAR national median for the building type.

## Inputs

- Annual energy use (kBtu, kWh, MWh, therms, GJ)
- Gross floor area (ft², m²)
- Building type (median site EUI, kBtu/ft²)

## Results

- Energy use intensity
- Compared with national median

## Formula

```
Site EUI = total annual site energy ÷ gross floor area
kBtu/ft² = kWh/ft² × 3.412; kWh/m² = kBtu/ft² × 3.155
```

## Explanation

Energy use intensity lets you compare the energy performance of buildings of different sizes. A lower EUI means better performance. ENERGY STAR Portfolio Manager publishes median EUIs for many building types, which give a useful benchmark.

### How to use the EUI Calculator

- **Annual energy use**
- **Gross floor area**
- **Building type (median site EUI, kBtu/ft²)**

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Enter the total energy the building used in a year (add electricity, gas and other fuels converted to the same unit), the gross floor area and the building type.

### Tips

- Use the figures from your own bills and product labels – prices and appliance ratings vary widely.
- Look at yearly totals: small daily costs add up and make it easier to compare options.
- Round quantities up to whole packs, rolls or bulbs when you shop.
- Re-check the numbers when prices change; most results scale directly with the unit price.

### Common mistakes to avoid

- Confusing watts (power) with watt-hours or kilowatt-hours (energy).
- Comparing prices without bringing them to the same unit first.
- Ignoring one-off costs such as installation, delivery or replacement parts.

### Inputs explained

FieldWhat to enterAnnual energy useUnits: kBtu, kWh, MWh, therms, GJGross floor areaUnits: ft², m²Building type (median site EUI, kBtu/ft²)Choose one: Office (52.9), Hotel (63.0), K-12 school (48.5), Hospital (234.3) …

### What each result means

- **Energy use intensity** = [Annual energy use]÷[Gross floor area]
- **Compared with national median** = ([Energy use intensity]÷[Building type (median site EUI, kBtu÷ft²)] - 1)×100

### Example values

How the main result changes when **Annual energy use** changes and everything else stays at the example values above:

Annual energy use (kBtu)Energy use intensity (kBtu/ft²/yr)100,00010150,00015200,00020250,00025300,00030400,00040

## Worked example

Inputs — Annual energy use: 200,000 kBtu; Gross floor area: 10,000 ft²; Building type (median site EUI, kBtu/ft²): Office (52.9).

Results — **Energy use intensity = 20 kBtu/ft²/yr**; Compared with national median = -62 %.

## Key terms

- **EUI**: Energy use intensity – annual energy divided by floor area.

## FAQ

**What is a good EUI for an office?**
The U.S. median for offices is about 53 kBtu/ft² per year; high performers are under 35.

**What is the difference between site and source EUI?**
Site EUI counts energy used on site; source EUI includes losses in generating and delivering it.

**How do I convert kWh to kBtu?**
Multiply by 3.412.

**What formula does the EUI Calculator use?**
Site EUI = total annual site energy ÷ gross floor area.


## Sources

- [ENERGY STAR Portfolio Manager – U.S. energy use intensity by property type](https://portfoliomanager.energystar.gov/)