A Calm Way to Choose Gerbil Tank Size for a Pair
Gerbil tank size advice splits between gallons and floor space, and one major charity gives no floor figure at all. Here is how to compare them.
Table of Contents
Why every site gives a different gerbil tank size
Published gerbil tank size figures for a pair of Mongolian gerbils run from about 1,300 cm² to 5,000 cm² of floor, because sources use different units, dates and standards. This guide sets each figure beside its source.
The short answer for a pair
Our target is Wood Green’s minimum for two gerbils: 100 × 50 × 50 cm (5,000 cm²). Merck’s older pet-owner rule works out near 1,300 cm².
Gerbils are social, so a pair is the starting point (see wheth A Calm Way to Choose Gerbil Tank Size for a Pairer gerbils can live alone). Own a smaller tank? The last section covers next steps.
What each source actually says for a pair
Each gerbil tank size figure below is the named publisher’s, for Mongolian gerbils.
| Source | For two gerbils | Floor (cm²) | Note |
|---|---|---|---|
| Merck Veterinary Manual | 10 gallons | about 1,290 | Reviewed May 2020 |
| Dakin Humane Society | 15 gallons, mesh lid | 1,858 | US shelter |
| Chewy article | 40 gallons | up to 4,181 | Retailer, unsourced |
| Galway SPCA | 100 × 50 cm | 5,000 | Rescue rule |
| Wood Green | 100 × 50 × 50 cm | 5,000 | UK charity, 2026 |
| RSPCA | none published | n/a | Height, bedding only |
Older rules and US figures
The Merck Veterinary Manual’s pet-owner page gives about 5 gallons per gerbil. A breed-society president told Chewy the rule has risen from 5 to 10 gallons per gerbil.
UK charities publish floor sizes in centimetres, while many US sources use gallons. Wood Green lists 120 × 50 × 50 cm for three gerbils.
🔄 Outdated Advice: Some retailer guides say the RSPCA recommends 40 gallons. The RSPCA’s gerbil housing page gives no floor figure, only height and bedding depth.
Why gallons are the wrong unit for gerbils
Gallons measure volume, but Mongolian gerbils live and dig on the floor, and Wood Green notes that floor space matters more than height. A 20-gallon high (24 × 12 in) gives 1,858 cm²; a 20-gallon long (30 × 12 in) gives 2,323 cm².
One tank-maker guide lists a 40-gallon at 36 × 12 in (2,787 cm²), yet a 40-gallon breeder (36 × 18 in) gives 4,181 cm².
Is a 20-gallon tank enough?
Even the long version gives only 46% of Wood Green’s floor, though it clears Merck’s 10 gallons and Dakin’s 15.
How real tanks compare with the 5,000 cm² target
Floor area is length times width, calculated by us from nominal tank-maker dimensions (1 in² = 6.45 cm²); we measured no tanks.
| Tank | Footprint | Floor (cm²) | Share of 5,000 |
|---|---|---|---|
| 10-gallon | 20 × 10 in | 1,290 | 26% |
| 15-gallon | 24 × 12 in | 1,858 | 37% |
| 20-gallon long | 30 × 12 in | 2,323 | 46% |
| 40-gallon breeder | 36 × 18 in | 4,181 | 84% |
| 100 × 50 cm tank | 100 × 50 cm | 5,000 | 100% |
| Ikea Detolf, on its back (Wood Green) | 163 × 43 cm | 7,009 | 140% |
Is a 40-gallon tank enough?
A 36 × 18 in breeder is about 16% under 5,000 cm², and other 40-gallon shapes have less floor.
How tall the tank needs to be, and what a topper does
For Mongolian gerbils, the RSPCA’s gerbil housing advice says a gerbilarium should ideally be about 50 cm high, with 20–30 cm of bedding, because an adult is about 12 cm tall.
A 40-gallon breeder is about 40.6 cm tall, so 30 cm of bedding leaves roughly 10.6 cm to the rim, less than that 12 cm. The pillar covers how deep the bedding should be.
Does a topper count toward tank size?
No. A topper adds headroom and ventilation above the bedding, not floor area.
How to pick a tank you can fit and keep clean
For two Mongolian gerbils, three steps turn the range into a choice.
- Measure the inside length and width of the base in centimetres.
- Multiply them and compare with the table: 5,000 cm² is our target.
- Choose the nearest tank at or above it, leaving 12 cm of height above the bedding.
✅ Do This: Measure unbroken floor, not shelves. Wood Green says floor space matters more than height and shelves.
The RSPCA recommends solid glass walls and does not recommend metal-bar cages.
Already have a 10 or 20-gallon tank? What to do now
Many owners of Mongolian gerbils start here, and Merck still gives 10 gallons for two. Multiply your tank’s inside length and width; if the floor is well under 5,000 cm², plan an upgrade rather than blaming yourself.
The RSPCA advises reusing a little unsoiled bedding when cleaning, because scent matters, so carrying some across may help.
Gerbil tank size questions, answered
1. How big should a gerbil tank be for two gerbils?
Published figures run from about 1,300 to 5,000 cm²; our gerbil tank target is Wood Green’s 100 × 50 × 50 cm.
2. Is a 20-gallon tank big enough for two gerbils?
It meets some US figures, but a 20-gallon long gerbil tank has 2,323 cm² of floor, under half of 5,000 cm².
3. Is a 40-gallon tank enough for two gerbils?
A 36 × 18 in 40-gallon breeder gives a gerbil tank 4,181 cm², about 16% under 5,000; other 40-gallon shapes have less.
4. Is a 10-gallon tank enough for two gerbils?
Merck gives 10 gallons for two, about 1,290 cm²; Wood Green’s gerbil tank minimum has roughly four times that floor.
5. Should I buy a gerbil tank by gallons or floor space?
Floor space: two 20-gallon tanks differ by about 25%, at 1,858 versus 2,323 cm², so compare gerbil tank footprints.
6. How tall should a gerbil tank be?
The RSPCA says ideally about 50 cm, allowing 20–30 cm of bedding plus room for an adult gerbil about 12 cm tall.
7. Does a tank topper count toward gerbil tank size?
No. A topper adds headroom and ventilation above the bedding, not floor area, so gerbil tank floor figures stay the same.
8. Can two gerbils live in a hamster cage?
The RSPCA recommends solid glass walls and does not recommend metal-bar cages, so a barred hamster cage is a poor fit.
9. Why do UK and US gerbil tank sizes differ?
UK charities use centimetres, many US sources use gallons, and one US breed-society figure rose from 5 to 10 gallons per gerbil.
10. Do three gerbils need a bigger tank than two?
Yes. Wood Green’s minimum gerbil tank for three is 120 × 50 × 50 cm, compared with 100 × 50 × 50 cm for two.
Measure first, then choose
Published gerbil tank sizes for a pair run from about 1,300 to 5,000 cm² because of units, dates and standards, not because gerbils differ. Our target is 100 × 50 cm of unbroken floor. Measure your tank’s base and compare it with the table above.
