What Size Cedar Hot Tub Do You Actually Need?

The size difference between AlumiTubs models is smaller than most people expect, and the differences in running cost, water use and wood consumption are modest once the tub is at temperature. The real decision is how many people you want to soak with comfortably, and whether you want room to host more. When in doubt, size up.

This guide covers the common assumptions about sizing, sets the record straight, and gives you a framework for the decision. It applies across the range, whether you are looking at a Wood Fired, a Hybrid or an Electric.

The three sizes at a glance

All three share the same construction: marine-grade aluminum interior, Canadian Western Red Cedar exterior, 360 degrees of insulation, and on Wood Fired and Hybrid the same internally submerged firebox. What changes is diameter and water volume.

Model	Diameter	Water	Wood Fired and Hybrid	Electric
Small	5 ft (1.5 m)	315 US gallons (1,200 L)	2 to 3 people	3 to 4 people
Standard	6 ft (1.8 m)	420 US gallons (1,600 L)	4 to 5 people	5 to 7 people
Large	7 ft (2.1 m)	650 US gallons (2,450 L)	6 to 8 people	9 to 10 people

The Electric seats more per size, because there is no firebox inside taking up room. All three are 38 inches (97 cm) deep as standard. A 44 inch (112 cm) depth is available on Wood Fired and Hybrid, and 44 or 48 inches (122 cm) on Electric.

One foot of diameter separates each model. That is a smaller physical difference than most people picture between a two-person tub and a group-sized one. If you are still weighing wood against electric or hybrid, the complete guide to heating options covers that decision first, since it changes the seating figures above.

Five misconceptions about hot tub size

1. Smaller tubs heat faster

True, though less dramatically than people expect. Water volume is one factor. Insulation quality, firebox design and heat retention all matter too, and every AlumiTub shares the same insulation and the same submerged firebox, the largest of its kind.

From a cold fill on a Wood Fired, the Small reaches soaking temperature in around two hours, the Standard in about three, and the Large in around five. That is a meaningful gap on the first heat. Once at temperature, all three hold heat similarly well, because the insulation is doing the same job across the range.

Heat-up time can be reduced at any size: dry seasoned hardwood, the lid and floating insulation on throughout, a warm fill where available, or running the electric side alongside the fire on a Hybrid. More in how long it takes to heat a wood fired hot tub.

2. Smaller tubs use much less water

Less, but not proportionally. Interior volume is reduced by the firebox and the seating, so the relationship between diameter and capacity is not linear: 315, 420 and 650 US gallons across the range.

How you manage the water matters more than which size you choose. A Large with filtration uses far less water across a season than a Small drained after every use. More in how often you should change hot tub water.

3. Smaller tubs use less wood

Once at soaking temperature, ongoing consumption is similar across all three. Heat retention is driven by insulation and the lid, not by water volume. Every size holds temperature on roughly an armful of wood a day, and with the lid in place a wood fired tub loses only two to three degrees Fahrenheit (about one to two degrees Celsius) overnight.

Wood quality matters far more than tub size. Dry seasoned hardwood transfers heat efficiently. Wet or green wood spends its energy on evaporation instead, whichever model you own. The best firewood to use goes through the options.

4. Smaller tubs take up much less space

Two feet of diameter separates the Small from the Large. What shapes the space requirement more is clearance for access on all sides, at least ten feet (3 m) of vertical clearance from the top of the chimney cap to anything overhanging on a Wood Fired or Hybrid, and whether you are adding the heating and filtration kit, which adds roughly a foot and a half on the side it attaches to.

If space is genuinely tight, the Small is the answer. If the question is only whether a Standard or a Large will fit, the difference is one foot. How to prepare for arrival covers siting and base preparation.

5. Smaller tubs cost significantly less

The gap is narrower than most people expect. Construction quality is identical across the range, and what you are paying for is the handcrafting, the pressure testing, the marine-grade aluminum and the warranted structure rather than volume of material.

It is worth being cautious about very low-cost alternatives at any size. A tub that depends on the wood swelling to seal needs ongoing attention and has a shorter service life, so the initial saving tends not to hold. More in cedar hot tubs, the pros and cons.

What actually differs between sizes

Factor	Meaningfully different?	Notes
Initial heat-up time	Yes	About 2 hr Small, 3 hr Standard, 5 hr Large from cold on a Wood Fired
Ongoing wood consumption	No	All sizes hold heat similarly once at temperature
Water per fill	Yes	315, 420 and 650 US gallons (1,200 / 1,600 / 2,450 L)
Filled weight	Yes	3,200 lbs (1,450 kg), 5,000 lbs (2,270 kg) and 7,000 lbs (3,175 kg). The figure that decides whether a deck needs work
Physical footprint	Modest	One foot of diameter between each model
Seating capacity	Yes	The most significant practical difference
Price	Modest	Less difference than most buyers expect

Depths of 44 and 48 inches add roughly 1,000 lbs (450 kg) to the filled weight, which is worth factoring into any deck calculation.

The case for sizing up

The first tubs built over twenty-five years ago are still in use, and the structure carries a 25 year structural warranty. When you will own something that long, the decision deserves a long frame.

The most common thing owners of smaller tubs say afterward is that they wish they had gone larger. Not because the Small is inadequate, but because circumstances change. A couple becomes a family. Friends visit more. The tub becomes a gathering point and the original calculation starts to feel tight.

Worth the year long wait. So glad I waited. I know I'll be enjoying my AlumiTub for decades to come.

Momo

Owners of larger tubs rarely say anything, because having more room than you occasionally need creates no problems.

If you are genuinely torn, go larger. The difference in day-to-day running is modest. The difference in what the tub allows over a lifetime is not. And nothing is locked in: size stays changeable at no charge until 30 days before your tub ships.

Conserving water, whichever size you choose

1. Fill from a natural source where you have one. Lake, river and ocean water all work with the marine-grade interior. Fill, soak, and return it. Ocean fills are changed every five to seven days rather than left standing, and the tub is rinsed between fills.
2. Add filtration if you soak often. One fill then holds for three to four months rather than a week or two.
3. Do not fill through a water softener. Softeners strip calcium as their entire function, and water low in calcium is chemically aggressive toward aluminum. Fill from an unsoftened tap, or bypass the softener.
4. Direct drained water to garden beds via the drain kit. Untreated water is fine for most garden use. Treated water needs neutralizing first.
5. Rinse off before getting in. Sunscreen, body oil and detergent residue are the main things that shorten water life.
6. Use the lid between soaks to cut evaporation and keep debris out.

Whichever size you choose, the water balance targets are the same. Alkalinity 80 to 120 ppm, adjusted first because it stabilizes everything else. pH 7.4 to 7.8. Calcium hardness 150 to 250 ppm. Bromine 2 to 3 ppm as the sanitizer, never above 3, never chlorine, and never a salt chlorine generator. The full routine is in how to keep hot tub water clean, and Good Clean Living Water Care is built around holding those numbers with as little sanitizer as possible.

The practical test

Lay a garden hose out in a circle at the diameter you are considering. Stand inside it with the people you will actually be soaking with, and adjust for how close together you want to sit.

That tells you more than any specification sheet. If you are still uncertain, email hi@alumitubs.com with your property and how you plan to use it, and we will tell you honestly what we would build, including when that is smaller than you were about to order. Or browse the full range: the Wood Fired, the Hybrid and the Electric.