# Box Volume Calculator (Rectangular Prism)

URL: https://speedycalculator.com/calculators/math/rectangular-prism/
Last updated: 2026-10-25

> The box volume calculator finds the volume, surface area and space diagonal of a rectangular box from its length, width and height, with conversion to litres, gallons and cubic feet.

## Inputs

- Length (m, cm, mm, km, in, ft, yd, mi)
- Width (m, cm, mm, km, in, ft, yd, mi)
- Height (m, cm, mm, km, in, ft, yd, mi)

## Results

- Volume
- Surface area
- Space diagonal

## Formula

```
V = l × w × h
Surface area = 2(lw + lh + wh)
```

## Explanation

Boxes, rooms, tanks and shipping cartons are all rectangular prisms.

### How to use the Box Volume Calculator

- **Length**
- **Width**
- **Height**
- Want to work backwards? Type a value into **Volume** and **Height** is calculated for you.

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

### How it works

Multiply the three dimensions for volume and add the areas of the six faces for surface area.

### Inputs explained

FieldWhat to enterLengthUnits: m, cm, mm, km, in, ft …WidthUnits: m, cm, mm, km, in, ft …HeightUnits: m, cm, mm, km, in, ft …

### What each result means

- **Volume** = [Length]×[Width]×[Height]
- **Surface area** = 2×([Length]×[Width] + [Length]×[Height] + [Width]×[Height])
- **Space diagonal** = sqrt([Length]^2 + [Width]^2 + [Height]^2)

### Example values

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

Height (m)Volume (m³)0.51.50.752.25131.253.751.54.526

## Worked example

Inputs — Length: 2 m; Width: 1.5 m; Height: 1 m.

Results — **Volume = 3 m³**; Surface area = 13 m²; Space diagonal = 2.69 m.

## FAQ

**How do I convert to litres?**
Choose L in the volume unit menu; 1 m³ = 1,000 L.

**Will a long object fit?**
Compare its length with the space diagonal.

**What formula does the Box Volume Calculator use?**
V = l × w × h.

**Can I work backwards from the result?**
Yes. Type the result you want into Volume and the calculator finds the matching height.