Free tool

Sugar syrup calculator

How much sugar, and how much water, for the feeder you own or the bag you have. The quantities are the National Bee Unit’s, which settles the old argument about whether two to one means by weight or by volume. Anything we worked out ourselves is marked as ours.

Which syrup?

Thick syrup, for autumn1 kg of sugar to 630 ml of water. Less water for the bees to dry out before winter.Thin syrup, for spring1 kg of sugar to 1,260 ml of water. More like a nectar flow, to get a colony building.

Work it out from

Syrup to make, in litres (the size of your feeder)

Thick syrup: the mix

White granulated sugar: 4.8 kg; The NBU’s quantity [NBU BPG 7a]
Hot water, not boiling: 3 litres; The NBU’s quantity [NBU FS 19]
Makes about: 6 litres of syrup; Our arithmetic on the NBU figures
Stored, it becomes about: 5.8 kg of stores; Our arithmetic: bees dry it to about the water of honey

In old money, 10.6 lb of sugar to 5.3 pints of water.

Making it

White granulated or caster sugar only. Brown and raw sugars cause dysentery. [NBU BPG 7a]
Add the water hot, not boiling, and stir until the syrup is clear. Boiling risks caramelising it.
Let it cool to hand warm before it goes in a feeder.
Make what you will feed in the next week or so. Syrup left standing grows mould. [NBU FS 19]
Feed in the evening and clear up any spill, so it does not start robbing. Bees may not be able to store syrup much beyond mid-October; after that, a light colony gets fondant. [NBU FS 19]

Where these figures come from

National Bee Unit, Feeding sugar to bees, best practice guideline 7a (November 2025)
National Bee Unit, Preparing honey bee colonies for winter, fact sheet 19 (June 2024)

The sugar and water are the NBU’s. How much syrup a mix makes, and how much stores it becomes, are our own arithmetic on their figures, and are labelled as ours above.

This is the mixing, not the feeding

How much a colony needs depends on what it already has, which only the colony can tell you.

Autumn feeding: about 20 kg, and how to get there covers working out what a colony is short of.
Making sugar syrup for bees has the mixes in full, and the two things never to feed.
Setting up to feed covers the feeder and the box it sits in.
Wasps at the hive is worth reading before syrup goes on in late summer.

Keep a note of what each colony took

A free Bees Knees Apiary account records every feed against its hive, next to the hive’s weight, so you can see which colonies are still light before the weather turns.

Create a free account