Marmalade Calculator

The classic UK ratio is 1kg Seville oranges to about 2kg sugar and roughly 2 to 2.5 litres of water (whole, unpeeled fruit weight). Delia Smith, Mary Berry and BBC Good Food all use 1kg fruit to 2kg sugar. This yields around 2.7 to 3kg of marmalade (about 6 to 7 one-pound jars). The high sugar content is essential: the finished preserve needs roughly 60% sugar for a reliable set and to keep safely. Under-sugaring risks a marmalade that will not set and will not store.

Yes, but sweet oranges have less pectin and acid than Seville oranges. Use a little less sugar (around 1.7x the whole-fruit weight) and add the juice of 2 lemons per kg of sweet oranges for pectin and acid to help it set. The flavour will be milder and sweeter. Note this calculator works from raw whole-fruit weight, not cooked pulp.

Seville oranges have a very short UK season, typically January to mid-February. Buy them when you see them and freeze whole if you cannot make marmalade straight away. They freeze perfectly and can be used from frozen.

The water is needed to soften the citrus peel before the sugar is added. The fruit simmers in water for 1.5-2 hours to make the peel tender. Most of this water evaporates during the subsequent boiling with sugar, which is why the final yield is much less than the total starting volume.

The setting point is 105C. Test by placing a teaspoon of marmalade on a cold saucer, letting it cool for a minute, then pushing it with your finger. If it wrinkles, it has reached setting point. Always remove the pan from the heat while testing to avoid over-cooking.