How this calculator works
There is no legal or universal standard for a home dog pen, so this calculator works from common practice: a floor area that grows with the size of the dog, a fence tall enough that the dog will not hop over it, and bars close enough that a head will not go through. Extra dogs add about 70% of the area each, because they can share the open floor.
Worked example: one medium dog in a 1.5 m by 1.2 m pen in the open has 1.8 m², against a recommended 2.0 (above the minimum, below the recommended). The fence is 910 mm high and needs 5.4 m of fencing, which is 8 panels plus a gate. A large dog needs 3.0 m² and 1,070 mm high fencing; two medium dogs need 3.4 m². Put the same pen in a corner and the fencing falls to 2.7 m.
Do not treat these as welfare limits. Kennel and shelter rules set their own minimum sizes for facilities, which are not meant for a home. Judge by the dog: it should lie out, turn round and move a few steps, and not be left shut in for long periods.
Assumptions and sources
The assumptions behind your numbers (waste, sizes, rates) are listed in the notes directly under your results, and they update when you change an input.
The formula and a worked example are shown above, so you can check any result by hand. Read how we calculate and check our numbers. Results are estimates for planning: supplier products vary, so check the size printed on the label.
Pen size and fence height by dog size
Planning values for one dog. Add about 70% of the area for each extra dog.
| Dog | Floor area | Fence height | Widest bar gap |
|---|---|---|---|
| Toy (under 5 kg) | 0.8 m² | 610 mm | 40 mm |
| Small (5 to 12 kg) | 1.2 m² | 760 mm | 50 mm |
| Medium (12 to 25 kg) | 2.0 m² | 910 mm | 75 mm |
| Large (25 to 40 kg) | 3.0 m² | 1,070 mm | 90 mm |
| Giant (over 40 kg) | 4.0 m² | 1,220 mm | 100 mm |
Tips before you buy
- A pen is not a cage. Plan the dog's day around it: a few hours at a time, with exercise and company either side.
- Put the bed away from the door and the water bowl and a toilet pad or a wee-wee area at the other end.
- Build the gate to open inwards onto a clear space, and fit a latch a dog cannot lift or push open.
- Smooth every edge and sand the timber. Dogs chew, so use a pet-safe finish or leave raw timber, and avoid chewable foam, plastic trim and exposed screws.
- Check the gaps between the bars, at the bottom as well as the top, so a head or a paw cannot get stuck.
Tools & materials for this project
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Frequently asked questions
How big should an indoor dog pen be?
For one medium dog, aim for about 2.0 square metres, with room for a bed, water and a toilet corner. Smaller dogs need less and large dogs more. Retail pens range from about 0.5 m² up to 4 m².
How tall should a dog pen fence be?
600 mm for toy dogs, 760 mm for small, 910 mm for medium, 1070 mm for large and 1220 mm for giant breeds. Add about 150 mm for a dog that jumps or climbs, and fit a lid if it still gets out.
How far apart should the bars be?
Close enough that the dog's head cannot pass through: about 40 mm for a toy dog and 75 mm for a medium dog, and narrower again for puppies.
Can I build a dog pen into a room?
Yes. A fitted pen against a wall or in an alcove saves fencing, and can be built to match the cabinets or shelves. Use the same rules for height, floor area and the gaps between bars, and keep the pen out of direct sun and draughts.
Do I need a gate?
Yes, unless the dog is lifted in and out. A gate 24 to 30 inches (60 to 75 cm) wide gets a person in with a bed and a bowl.
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Related calculators & guides
Estimates only. Results assume standard materials and simple shapes. Supplier products vary, and the final call on quantity, structure and safety is yours. Check your local code and your supplier's guidance before ordering.