On paper a 5 metre bell tent only appears to be slightly larger than a 4 metre. There is however a big difference in the square meter / square footage of the tents.
Bell tents are (almost) a circle so the area is determined by the radius rather than the width.
4 metre area = 12.5664 m2/139.934 ft2
5 metre area = 19.635 m2/213.41ft2
A 5 metre bell tent is therefore 56.25% larger than a 4 metre.
To put this in real terms you could:
In a 4 metre accommodate 2 double mattresses and still have room for a living/luggage area.
In a 5 metre comfortably have 3 double mattresses and still have a lot of room for a living/luggage area at the front or have 4 double mattresses without a living area.
4 Metre bell tent with two standard, double air beds with living/lounge area at front.
5 metre bell tent with 3 double air beds and Large living/lounge area at front (or have 4 double air beds with no area at front)
The 4 metre bell tent net weight (weight with packaging etc) is 28 kg with a gross weight 27kg (our bell tents are heavier than the average due to our heavy duty poles and pegs and also our additional set of stake pegs for the elastic loops)
The 5 metre bell tent has a net weight of 36 kg with a gross weight of 37 kg
A four metre weighs 10 kg less than the 5 metre so it is quite a bit easier to carry.
- Lighter to carry (9kg less weight makes a lot of difference)
- More stable in heavy winds (our super thick poles/extra pegs/strong guys also help)
- Easier to heat and stay warm (extend the camping season into the winter months)
- Faster to set up
- Easier to store
- Less money
- More practical on campsites with small pitch sizes
- More room!
So which size?
Of course its all a personal choice what size you go for, but as a general rule:
If you are regularly sleeping two people, and occasionally four, a 4 metre may be better suited because it takes less time to set up , it is less expensive, packs down smaller and it is lighter to carry.
If regularly sleeping 4 + people, or if you are planning on going on extended week long + camping trips where set up time/carry weight is not such an issue, a 5 metre may be better suited as it gives you that extra room.
If regularly sleeping 3 people either size is fine. However, on balance a 5 metre may be better suited as I would suggest that having slightly more space than you need is not a bad situation to be in.