What washing machine capacity do I actually need?

The kilogram figure on a washing machine is the weight of dry cotton the manufacturer says the drum will wash properly. Nobody weighs laundry, and almost nobody washes pure cotton, so the number is hard to translate. What makes it useful is turning it around: instead of asking what capacity suits your household, ask what the largest thing you need to wash at home is, because that single item sets the floor.

What you'll need

• A rough idea of what you currently wash in a week
• The size of your largest duvet

Step by step

1. Start with your bulkiest regular item.A single duvet needs roughly a 7kg drum, a double roughly 8kg, a king roughly 9kg and a super king 10kg or more. Bulk matters more than weight here — a duvet is light and enormous, and it needs room to move or it does not get clean.
2. Then sanity-check against your weekly clothing volume.As a rough guide, 7kg is about two or three loads a week for one or two people, 8kg covers a family of four, and 9 to 10kg suits a household doing laundry most days or washing a lot of bedding.
3. Understand that the rating is dry cotton, not a mixed load.Towels are dense and hit the weight limit while the drum still looks half empty. Duvets and synthetics fill the drum long before they hit the weight. Whichever comes first is your real limit.
4. Load by volume in practice, not by weight.Fill the drum loosely to about three quarters and check a flat hand slides in on top. That is the working limit for any load, whatever the rating says, because clothes have to fall through the water for the wash to happen at all.
5. Do not size down to save energy.Modern machines weigh the load and adjust water and time accordingly, so a half load in a big drum uses far less than a full cycle. The old advice to buy small to avoid waste has not been true for well over a decade.
6. Check the drum depth, not just the kilogram figure.Two machines rated the same can have noticeably different drum volumes in litres, which is the number that actually decides whether a duvet fits. Where the litre figure is published, it is more honest than the kilogram one.
7. Consider the alternative before buying a very large machine.If a king-size duvet is the only thing that will not fit, two launderette trips a year may be cheaper and easier than a 10kg machine that is deeper than your worktop.

Tips

• Washing a duvet in a drum that is too small does not just wash it badly — the sodden weight on one side of the drum is exactly what the balance sensor refuses to spin, so you get a soaking duvet and an aborted cycle.
• Capacity ratings are given for cotton because cotton is dense. If most of your wash is synthetic sportswear, you will fill the drum by volume long before the rated weight, and the rating overstates what the machine will do for you.
• A larger drum on the same footprint usually means a shallower door seal and a slightly larger door aperture, which makes loading and unloading noticeably easier.

Common mistakes

• Choosing capacity from a household-size chart alone — It ignores bedding, which is the item that actually decides whether the machine is big enough. A couple with a super king duvet needs a bigger machine than a family of four with singles.
• Filling to the rated weight — The rating is a laboratory maximum for dry cotton. In practice a drum should be loosely three-quarters full, and a packed drum washes and rinses badly regardless of what the sticker says.

Questions people ask