By weight and by volume are two different recipes
Syrup ratios for bees are conventionally given by weight. A 1:1 syrup means a pound of sugar to a pound of water, and since a pint of water weighs almost exactly a pound, that has always been easy enough to do with a kitchen scale or even a measuring jug of water. A 2:1 syrup means two pounds of sugar to one pound of water. Those give 50 percent and 66.7 percent sugar by weight respectively.
Measured by volume instead, the same names give something else. Granulated sugar has a bulk density of roughly 0.85 g/mL against water at 1.00, because a cup of sugar is mostly sugar crystals with air between them. A US cup of granulated sugar weighs about 200 g while a cup of water weighs about 237 g. So a 1:1 volume mix is 45.8 percent sugar by weight, not 50, and a 2:1 volume mix is 62.9 percent rather than 66.7. Both are thinner than the name implies, and the gap widens as the ratio gets thicker.
| Nominal ratio | By weight | By volume |
|---|---|---|
| 1:1 | 50.0% sugar | 45.8% sugar |
| 1.5:1 | 60.0% sugar | 55.9% sugar |
| 2:1 | 66.7% sugar | 62.9% sugar |
Neither is wrong so long as you know which one you made and stay consistent, and volume is genuinely more convenient for a small batch. What causes trouble is switching between them without noticing, so that a batch you think you are repeating comes out different, and then attributing the difference to the weather.
Why two ratios exist at all
The thin syrup and the thick syrup do different jobs, and beekeepers have used both for a very long time. A 1:1 syrup is close in concentration to nectar, and colonies handle it the way they handle a nectar flow. A 2:1 syrup carries nearly twice the sugar per unit of water, which means the bees have far less water to drive off before it can be capped and stored, and it takes up less room in a feeder for the same amount of food. That is the whole distinction: how much water comes with the sugar and how much work it takes to remove it.
What follows from that in your apiary — whether to feed, which syrup, when in the season, and how much — is not something a calculator can decide, and honest sources will not tell you either. It depends on the length and character of your winter, what is blooming near you and when, the size and condition of the individual colony, and what is already in the boxes. A beekeeper thirty miles away with the same equipment may reasonably do something different. Your local association, an experienced beekeeper in your county and your state apiary program are the sources for that judgement, and they are worth finding before the season you need them.
Volume does not behave the way you expect
Sugar dissolved in water does not disappear into it. It adds substantially to the total volume, which catches people out when they mix a batch in the container they intend to feed from. Start with five pounds of water, which is 0.6 gallons, add ten pounds of sugar to make a 2:1 batch by weight, and you finish with about 1.35 gallons of syrup. The volume has more than doubled. Mix a two-gallon batch of 2:1 in a two-gallon bucket by putting the water in first and you will be cleaning the floor.
This calculator handles it either way. Size the batch by the finished syrup you want and it works backwards to the sugar and water. Size it by the sugar you have in the bag and it tells you what volume that becomes. Size it by the water and it does the same from the other end.
The limit at the top of the range
Sucrose will dissolve in water up to roughly 67 percent by weight at room temperature. A 2:1 syrup by weight sits right at that ceiling, which is why it needs hot water to go into solution and why it throws crystals in a cold feeder or a bucket left in an unheated shed. Nothing is wrong when that happens; the syrup has simply cooled past what it can hold. Warming and stirring puts it back. Going deliberately thicker than 2:1 by weight means making something that will not stay in solution at all, and there is no advantage in it.
Use plain white granulated sugar. Brown, raw and unrefined sugars, molasses and anything with additives contain solids that bees cannot process, and they cause problems rather than adding nutrition. Never feed honey bought in a shop or given by another beekeeper, because honey can carry disease between colonies and there is no way to tell by looking. If your sugar arithmetic is for brewing rather than bees, the priming sugar calculator is the one you want.
Once syrup is in the hive, what it becomes is a weight question, and the winter hive weight calculator separates stored food from equipment so you can see it on a scale.
Questions people ask
Is 2:1 sugar syrup measured by weight or by volume?
By weight, conventionally. Two pounds of sugar to one pound of water, which gives 66.7 percent sugar by weight. Plenty of beekeepers mix by volume instead because it is faster, and two cups of sugar to one cup of water is a perfectly usable syrup, but it is 62.9 percent rather than 66.7 because a cup of sugar weighs less than a cup of water. The practical advice is to pick one method and never switch, so that your batches are repeatable. If you are following someone else's instructions and they do not say which basis they mean, assume weight, and assume the difference matters more to the record you keep than to the bees.
Why does my 2:1 syrup crystallise in the feeder?
Because it is close to saturated. Water will hold roughly 67 percent sugar by weight at room temperature, and a 2:1 syrup by weight is 66.7 percent, so it is sitting right at the limit. Warm water dissolves more, which is why a 2:1 batch mixes easily when hot and then drops crystals as it cools, particularly in a cold feeder or a bucket stored in an unheated space. Warming and stirring puts it back into solution. If it is a recurring nuisance, mixing slightly thinner, at say 1.75:1, costs you very little concentration and stays in solution much more reliably.
How much syrup will a batch actually make?
More than the water you started with, by a lot. Dissolved sugar contributes its own volume rather than fitting into the spaces between water molecules. Ten pounds of sugar in five pounds of water, a 2:1 batch by weight, makes about 1.35 gallons of syrup from 0.6 gallons of water. Eight pounds of sugar in eight pounds of water, a 1:1 batch, makes about 1.56 gallons from 0.96 gallons of water. This is why mixing in the feeder is a mistake and why the calculator lets you size the batch by the finished volume rather than by the ingredients.
Can I use brown sugar, raw sugar or honey?
No. Plain white granulated sugar is what to use, and the reason is not fussiness. Brown, raw, unrefined and organic sugars retain solids and minerals that bees cannot digest and cannot excrete while confined, and the same applies to molasses and to anything marketed as a sugar substitute. Honey is a separate and more serious problem: it can carry disease spores between colonies, and honey from a shop may have come from anywhere. Feeding a colony honey that did not come from that colony is a well-established way to move disease around, so it is not a shortcut worth taking even when the honey is free.
When should I feed and how much?
That is not a question this calculator answers, and be sceptical of any source that answers it confidently without knowing where you are. Feeding decisions turn on the length of your winter, when your flows come and end, what is planted around you, how strong the colony is, how much is already stored and whether the colony can even take syrup down at the temperature it is. Those vary enormously between regions and between two colonies in the same yard. The people to ask are your local beekeeping association, an experienced beekeeper in your county and your state apiary program, and all three are more useful before you need them than after.