Steam Generator Size Calculator
Part of our Home Spa & Outdoor guides.
Estimate the steam generator size for your shower.
How it works
Volume = length × width × height. Tile and stone absorb heat, so we multiply the volume by 1.5 for tile and 2 for stone to get an effective volume, a common sizing approach. Always check the manufacturer's room-size rating.
Worked examples
- 3x4x8 ft acrylic shower: 96 ft³ → 4 kW class.
- 5x4x8 ft tiled shower: 160 ft³ × 1.5 = 240 effective → 9 kW class.
- 6x5x9 ft stone shower: 270 ft³ × 2 = 540 effective → 15 kW or larger.
Other factors
- Exterior walls and large windows lose heat; size up.
- Ceilings above 8 feet add volume and stratification.
- Rooms where the steam head is far from the generator lose some performance.
Before buying
Confirm the enclosure is vapor-tight to the ceiling, the ceiling slopes, and you have a 240 V circuit of the size the generator requires.
Frequently asked questions
Why does tile need a bigger generator?
Tile and stone absorb heat, so more steam is needed to warm the room.
How do I measure a shower with a sloped ceiling?
Use the average ceiling height: add the lowest and highest heights and divide by two, then multiply by length and width.
Does a bench count toward volume?
A tiled bench adds thermal mass rather than air volume. Many people ignore it for volume but size up slightly for the extra tile.
Can a generator be too big?
A slightly larger unit heats faster, but a much larger one needs a bigger circuit and costs more. Aim for the size that covers your effective volume with a small margin.
What if my result is between two sizes?
Choose the larger size, especially for tiled or stone rooms, exterior walls or high ceilings.