# Bath vs Shower Calculator

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

> The bath vs shower calculator compares how much water – and money – a shower and a bath use, from the shower's flow rate and length and the size and fill level of your tub, per wash and per year.

## Inputs

- Shower flow rate (gpm, L/min)
- Shower length (min)
- Bathtub capacity (L, US gal)
- Bath fill level
- Body weight (kg, lb, g)
- Washes per week
- Water and sewer price (/m³, /1000 US gal)
- Cost to heat 100 L of water

## Results

- Water per shower
- Water per bath
- Bath minus shower
- Showers – water per year
- Baths – water per year
- Showers – cost per year
- Baths – cost per year

## Formula

```
Shower water = flow rate × minutes
Bath water = tub capacity × fill level − water displaced by your body (≈ body weight ÷ 1 kg/L)
Yearly = per wash × washes per week × 52.18
```

## Explanation

A full bath uses about 80–150 litres of water, while a standard shower uses about 9 litres (2.4 gallons) a minute and a low-flow head 6 litres. So a quick shower almost always uses less – but a long power shower can use more than a bath. Heating that water is usually the bigger cost.

### How to use the Bath vs Shower Calculator

- **Shower flow rate**
- **Shower length**
- **Bathtub capacity**
- **Bath fill level**
- **Body weight**
- **Washes per week**
- **Water and sewer price**
- **Cost to heat 100 L of water**

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

### How it works

Enter your shower's flow rate and typical length, the tub capacity and how full you fill it, your body weight, how many times a week you wash, and your water and energy prices.

### Tips

- Use the amounts printed on the product (ml, sheets, applications) where available.
- Count everyone in the household who shares the product.
- Buy a little extra so you never run out unexpectedly.
- Small daily habits add up – check the yearly figures for the real impact.

### Common mistakes to avoid

- Forgetting that hot water costs energy as well as water.
- Underestimating how much sunscreen a full application needs.
- Comparing pack prices without checking the size of each pack.

### Inputs explained

FieldWhat to enterShower flow rateUnits: gpm, L/minShower lengthIn minBathtub capacityUnits: L, US galBath fill levelChoose one: Full, Three quarters, About 60%, Half …Body weightUnits: kg, lb, gWashes per weekA numberWater and sewer priceUnits: /m³, /1000 US galCost to heat 100 L of waterAmount in your currency

### What each result means

- **Water per shower** = [Shower flow rate]×[Shower length]×60
- **Water per bath** = max([Bathtub capacity]×[Bath fill level] - [Body weight]÷1000, 0)
- **Bath minus shower** = [Water per bath] - [Water per shower]
- **Showers – water per year** = [Water per shower]×[Washes per week]×52.18
- **Baths – water per year** = [Water per bath]×[Washes per week]×52.18
- **Showers – cost per year** = [Showers – water per year]×([Water and sewer price] + [Cost to heat 100 L of water]×10)
- **Baths – cost per year** = [Baths – water per year]×([Water and sewer price] + [Cost to heat 100 L of water]×10)

### Example values

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

Shower flow rate (gpm)Bath minus shower (L)1.2542.11.8723.22.54.33.12-14.63.75-33.65-71.4

## Worked example

Inputs — Shower flow rate: 2.5 gpm; Shower length: 8 min; Bathtub capacity: 200 L; Bath fill level: Three quarters; Body weight: 70 kg; Washes per week: 7; Water and sewer price: $4 /m³; Cost to heat 100 L of water: $0.6.

Results — Water per shower = 75.7 L; Water per bath = 80 L; **Bath minus shower = 4.3 L**; Showers – water per year = 27.7 m³; Baths – water per year = 29.2 m³; Showers – cost per year = $276.53; Baths – cost per year = $292.21.

## FAQ

**Does a shower use less water than a bath?**
Usually – an 8-minute shower at 2.5 gpm uses about 76 L, while a 60%-full bath uses 100–120 L.

**How much water does a bath use?**
80–150 L (20–40 gallons) depending on the tub and how full you fill it.

**How can I use less water in the shower?**
Fit a low-flow head (1.5–1.8 gpm) and keep showers under 5 minutes.

**What formula does the Bath vs Shower Calculator use?**
Shower water = flow rate × minutes.


## Sources

- [U.S. EPA WaterSense – Showerheads](https://www.epa.gov/watersense/showerheads)