There are about 5.26 cups in a kilogram of caster sugar. That is the short answer, and it is the number this page is built around: one US cup of caster sugar weighs 190 g spooned and levelled, according to King Arthur Baking, so 1,000 g divided by 190 g gives 5.26 cups. Every figure on this page is approximate, because cup weights shift a little with how the cup is filled, and when the result matters — a cake, a brine, a batch of jam — a kitchen scale is the only way to be exact.

Caster Sugar is fine-grained white sugar that dissolves faster than granulated sugar. It is used for meringues, cocktails, shortbread and custards. That is why the kilogram-to-cups question comes up so often: caster sugar is sold by weight in most countries, while many recipes — especially American ones — measure it in cups. This page converts the whole kilogram, not just a single cup, so you can plan a whole bag or tub against a recipe instead of converting one spoonful at a time.

Conversion table: kilograms of caster sugar to cups

One US cup is 236.6 ml, and one cup of caster sugar weighs 190 g spooned and levelled. Every row below is that cup weight divided into the weight shown, so the whole table follows from a single number. Figures are rounded to two decimal places and labelled approximate.

Weight Cups (approx.)
100 g 0.53
250 g 1.32
500 g 2.63
750 g 3.95
1 kg (1,000 g) 5.26
1.5 kg (1,500 g) 7.89
2 kg (2,000 g) 10.53

The same cup weight works in the other direction too:

Measure Weight (approx.)
1 cup 190 g
1 tablespoon 11.9 g
1 teaspoon 3.96 g
1 kg in tablespoons about 84 tbsp

If you only need part of the kilogram, the table above is the fastest way to read it off. Half a kilogram is 2.63 cups, a quarter is 1.32 cups, and 100 g — a common recipe amount — is 0.53 cups.

How the figure is worked out

The calculation is a single division: 1,000 g ÷ 190 g per cup = 5.26 cups. The only input is the weight of one cup of caster sugar, and that comes from King Arthur Baking, which lists one US cup of caster sugar at 190 g, spooned and levelled. The confidence rating on that figure is high, which means it is a published, checked value rather than an estimate — but it is still a cup measurement, and cups are never as exact as grams.

Spooned and levelled means spooning caster sugar loosely into the cup and sweeping the top flat with a knife, never scooping the cup through the bag. Scooping packs the ingredient down and can add 10–20% to the weight, which is exactly how a recipe ends up with too much of something and nobody knows why.

That is also why every number here carries the word approximate. A cup is a volume measure being used as a stand-in for weight, and the two only line up when the filling method matches the published one. If the dish is forgiving — a stew, a marinade, a crumble topping — the cup figure is plenty. If it is a cake, a loaf of bread, or anything where a 10% error changes the texture, weigh the ingredient on a kitchen scale and skip the cups entirely.

Worked examples

The table is useful, but recipes do not come in kilograms. Here are three ordinary situations where the kilogram-to-cups figure does real work.

Example 2 — doubling a cookie batch

Your cookie recipe uses 1½ cups of caster sugar (285 g) and you want to double it for a school bake sale. Doubled, that is 3 cups, or 570 g — about 57% of a kilogram bag. Weighing 570 g straight from the bag is faster and more accurate than scooping three cups, and you still have 2.26 cups in reserve.

Example 3 — a glaze measured in grams

A glaze recipe lists 100 g of caster sugar rather than cups. That is 0.53 cups — just over half a cup, or about 8.4 tablespoons. Measuring the glaze by weight avoids the common mistake of packing a cup too firmly and ending up with a glaze that sets too sweet and too thick.

Example 1 — a cake from a 1 kg bag

A sponge cake calls for 2 cups of caster sugar. Two cups weigh 380 g, so from a 1 kg bag you use just over a third of it and have about 3.26 cups left — enough for a second, smaller bake. If you are making the same cake again next weekend, one bag covers roughly 2.6 two-cup cakes before it runs out.

Measuring it well, and storing what is left

The most common mistake with caster sugar is the packing question. Spooned and levelled is the method behind every figure here, and changing the method changes the weight. A cup scooped hard from the bag can weigh 10–20% more than a spooned-and-levelled cup, which in a cake means a sweeter, denser crumb and a bake that browns too fast. The second mistake is measuring over the mixing bowl: spill a little extra in and there is no way to take it back. Measure over the bag or a plate instead.

Storage matters once you have opened a kilogram pack. Airtight container, cool and dry, indefinitely. A kilogram is a lot of caster sugar for a home kitchen — for most households it will last weeks or months — so decanting it into a sealed container on the day you open it is worth doing: it keeps the weight stable, keeps moisture out, and means the cup you measure in a month weighs the same as the cup you measure today.

Without a scale, tablespoons are the fallback: one kilogram of caster sugar is about 84 level tablespoons, and one cup is 16 tablespoons, so you can build any amount in the table above from spoonfuls. It is slower than weighing, and each spoonful adds its own small error, but for soups, marinades, and everyday cooking it is close enough. For baking, borrow or buy a scale — it is the single cheapest upgrade to a home baker's accuracy.

Buying it by the kilogram

Shops sell caster sugar by weight, and the kilogram is the standard pack size in most countries outside the United States. Knowing that the pack holds about 5.26 cups lets you compare it honestly against smaller packs: a 500 g pack is 2.63 cups, so if the kilogram costs less than twice the 500 g price, it is the better buy — provided you will use it before it goes stale. For caster sugar, meringues, cocktails, shortbread and custards. Work out how many cups your household actually uses in a month before choosing the big pack; a bargain that ends up thrown away is not a bargain. And remember the figure is approximate: if the recipe on the packet is written in grams, follow the grams. Cups are a translation, not the original.

Frequently asked questions

How many cups are in 1 kg of caster sugar?

About 5.26 cups. One cup of caster sugar weighs 190 g spooned and levelled (King Arthur Baking), and 1,000 g ÷ 190 g = 5.26 cups. The figure is approximate, because how firmly the cup is filled changes the weight slightly.

How many tablespoons are in 1 kg of caster sugar?

About 84 level tablespoons. One tablespoon of caster sugar weighs 11.9 g, so 1,000 g divided by that is 84 spoonfuls. Tablespoons are a workable fallback when there is no scale, but each spoonful adds a little error, so weigh when it matters.

Can I use the same cups-per-kilogram figure for other brands of caster sugar?

Usually, yes, within a small margin. The cup weight of a standard ingredient is set by its density, which barely changes between brands. What does change it is the form — fine versus coarse, sifted versus settled, softened versus fridge-hard — so if a brand feels noticeably lighter or denser in the hand, weigh a cup of it once and use your own figure.

How should I store a kilogram of caster sugar once it is open?

Airtight container, cool and dry, indefinitely. A kilogram is a large pack for most kitchens, so an airtight container is worth the effort: it keeps moisture out and keeps the cup weight stable over the weeks it takes to use it up.

Does a kilogram of caster sugar weigh the same as a litre of it?

Only if its density is close to water's. A litre is 1,000 ml, and one US cup is 236.6 ml, so a litre is about 4.23 cups by volume. A kilogram of caster sugar is 5.26 cups by weight, which is a different question — the two match only for ingredients whose cup weighs about 237 g. For most ingredients they do not, which is exactly why weight and volume conversions need a density figure.

Related conversions

More conversions for caster sugar, and the tools that do this arithmetic for you: