Sugar syrup for bees calculator
How much sugar and water for your hives? Choose the syrup, then the quantity or the number of colonies. Everything is worked out by weight, the way the National Bee Unit gives its recipes, with pounds and pints alongside.
How it is calculated
Recipes by weight
The NBU’s thick syrup is 1 kg of white granulated sugar dissolved in 630 ml of water (2 lb to 1 pint) and its thin syrup 1 kg in 1,260 ml (2 lb to 2 pints). Many associations write the same idea as 2:1 and 1:1 by weight: 2 kg of sugar to 1 litre of water, and 1 kg to 1 litre. The Scottish Beekeepers Association’s heavy syrup sits in between, at 1 kg to 600 ml (62.5 %). A cup of sugar to a cup of water makes a weaker syrup than any of these, because granulated sugar is lighter than water by volume: always weigh it.
The formulas
syrup weight = volume × density
sugar = syrup weight × sugar fraction
water = syrup weight − sugar (1 kg of water = 1 litre)
volume = syrup weight ÷ densityIn “per colony” mode the volume is colonies × syrup per colony. In “sugar I have” mode the syrup weight is sugar ÷ sugar fraction.
| Syrup | Sugar by weight | Density | Sugar in 1 litre | Syrup from 1 kg of sugar |
|---|---|---|---|---|
| NBU thick syrup: 1 kg sugar to 630 ml water | 61.3 % | 1.3 kg/L | 0.8 kg | 1.26 L |
| NBU thin syrup: 1 kg sugar to 1,260 ml water | 44.2 % | 1.2 kg/L | 0.53 kg | 1.88 L |
| 2:1 by weight: 2 kg sugar to 1 litre water | 66.7 % | 1.33 kg/L | 0.89 kg | 1.13 L |
| 1:1 by weight: 1 kg sugar to 1 litre water | 50 % | 1.23 kg/L | 0.62 kg | 1.62 L |
| Ready-made invert syrup (Ambrosia, Invertbee) | 72 % | 1.37 kg/L | 0.99 kg | 1.01 L |
Densities are those of a sucrose solution at 20 °C from standard sucrose tables, rounded; for the ready-made syrup we use the Invertbee specification (72 to 73 % solids, 1.37 kg per litre), and Ambrosia states a feed value of about 72.7 %. Worked example: 10 kg of sugar in 6.3 litres of warm water gives 16.3 kg, about 12.6 litres, of NBU thick syrup, enough for a colony 10 kg short of its winter stores with a little to spare.
Safe syrup
Use white granulated or caster sugar only, cane or beet. Never boil syrup and never add vinegar, lemon juice or cream of tartar: heat and acid form HMF, which is toxic to bees. Feed in the evening, all colonies on the same night, with entrances reduced, and never with honey supers on: syrup stored in supers would end up in your honey, and honey sold as honey may contain nothing added. The 20 kg target, the feeding calendar and the feeders are explained in our guide to feeding bees. For winter, use the fondant calculator.
Frequently asked questions
What is the ratio of sugar to water for bee syrup in the UK?
The National Bee Unit uses 1 kg of white granulated sugar to 630 ml of water for thick syrup, the old 2 lb to 1 pint, and 1 kg to 1,260 ml for thin syrup. Many associations simply say 2:1 and 1:1 by weight. Weigh the sugar rather than measuring it by the cup.
Is 2:1 syrup the same as NBU thick syrup?
Nearly. NBU thick syrup, 1 kg of sugar to 630 ml of water, is about 61 % sugar by weight. A true 2:1 by weight, 2 kg of sugar to 1 litre of water, is about 67 %. Both work for autumn feeding; the 2:1 mix carries a little more sugar per litre but is slower to dissolve.
How much sugar syrup does a hive need for winter?
The NBU says a colony needs 18 to 22 kg of stores to get through winter and sets about 20 kg in autumn as the working target. Estimate what the hive already holds, then plan roughly 1 kg of sugar for each kilogram missing: a 10 kg shortfall means about 12.5 litres of thick syrup.
Can I use brown sugar or icing sugar for bee syrup?
Use white granulated or caster sugar only. The NBU warns that brown and raw sugars contain impurities that cause dysentery in bees confined to the hive in winter. Cane or beet makes no difference. Icing sugar often contains an anti-caking agent, so it is better kept for fondant recipes that call for it.
Should I boil the water for sugar syrup?
No. Warm water dissolves the sugar quickly, but never boil the syrup or add vinegar, lemon juice or cream of tartar. Heat and acid turn sugars into hydroxymethylfurfural (HMF), which the European Food Safety Authority found harmful to bees. Let hot tap water or a kettle do the work, and stir.
Is Ambrosia or Invertbee better than homemade syrup?
They are ready to use invert syrups, about 72 % sugar, that stay liquid and need no mixing, which saves time with many hives. Bees do as well on homemade thick syrup. A 12.5 kg can of Ambrosia holds about 9 kg of sugar, so per kilo of sugar it costs several times granulated sugar.
When should I stop feeding syrup in autumn?
Aim to finish in September or early October while days are mild enough for the bees to take the syrup down, evaporate it and cap it. The NBU warns against feeding syrup in cold weather, when bees cannot process it. If a colony is still light at the end of October, give fondant over the cluster instead.
Sources
- Feeding bees: sugar (Best Practice Guideline No. 7a, November 2025), Animal and Plant Health Agency, National Bee Unit
- Feeding bees (BBKA News, August 2012, pp. 7 to 8), National Bee Unit, APHA
- Preparing your hives for winter (Fact sheet 19), Animal and Plant Health Agency, National Bee Unit
- Technical Data Sheet 1: heavy syrup feeds (August 2023), Scottish Beekeepers Association
- Recipes for feeding to bees, Dorchester and Weymouth Beekeepers Association
- Sucrose conversion table (Appendix XV): apparent specific gravity at 20 °C, USDA Agricultural Marketing Service
- Ambrosia bee food syrup: product specification, Ambrosia, Nordzucker
- Invertbee syrup 28 kg / 20 L: product description, Simon the Beekeeper
- Invertbee bee feeding syrup 14 kg: specification (72 to 73 % dry matter, 1.37 kg/dm³), Bienenzuchtbedarf Geller
- Risks for animal health related to HMF in feed for honey bees (EFSA Journal 2022;20(4):7227), European Food Safety Authority
Calculators
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