By the Dolca Team
Short answer: the best caster (or castor) sugar substitute is superfine sugar, because caster sugar and superfine sugar are the same thing. No superfine on hand? Use the same weight of regular granulated sugar, or pulse it in a dry blender for a few seconds to make it finer. That works in almost every cake, cookie and dessert.
We make sugar, so we will be upfront: most of the time, the sugar already in your pantry will do the job. Below we cover every option honestly, including when you do not need anything special, and when a superfine sugar like Dolca Slim or Organic Dolca Slim is worth it.
- Superfine sugar: the closest match, because it is the same thing. Use 1:1.
- Granulated sugar: the simplest swap for most cakes and cookies. Measure by weight.
- Homemade caster sugar: granulated sugar pulsed briefly in a dry blender, for meringues and delicate sponges.
- Cane sugar: yes, it works. Caster sugar is simply sugar with finer crystals.
- Dolca Slim and Organic Dolca Slim: superfine prebiotic cane sugar, conventional or USDA organic, for easy 1:1 sugar swaps, with the same sweet taste, 25% less sugar by equal weight, fewer calories and 2g prebiotic fiber per 8g serving.
- Golden caster sugar: use raw cane sugar or Dolca Raw Slim, pulsed fine.
- Dolca Panela: for recipes calling for brown sugar, with warm caramel flavor.
- Powdered sugar: best kept for frostings and glazes, not a direct caster sugar replacement.
What is caster sugar?
Caster sugar (sometimes spelled castor sugar) is sugar with very fine crystals. In the United States you will usually see it sold as superfine sugar or baker's sugar. It is just as sweet as regular granulated sugar; only the crystal size is different.
It sits between two familiar sugars:
- Granulated sugar: larger crystals, the everyday pantry sugar.
- Caster (superfine) sugar: finer crystals that dissolve more quickly.
- Powdered sugar: ground to a powder, usually with a little starch added to prevent clumping.
Because the chemistry is the same as granulated sugar, the real question is how much the fine texture matters in your recipe.
Why do recipes call for caster sugar?
Fine crystals dissolve faster. That matters most when there is little liquid or little time for the sugar to melt into the mixture.
- Meringues and pavlova: sugar needs to dissolve into whipped egg whites for a smooth, glossy finish.
- Sponge and chiffon cakes: fine sugar creams and whisks in easily for a light, even crumb.
- Shortbread and butter cookies: a finer sugar gives a more delicate, tender bite.
- Whipped cream, mousse and cold drinks: fine crystals avoid a gritty texture.
Many British and Australian recipes use caster sugar as their everyday white sugar. In those recipes, granulated sugar usually works well.
What can I use instead of caster sugar?
Here are your options, from easiest to most specific:
| Substitute | Best for | What it brings | Keep in mind |
|---|---|---|---|
| Granulated sugar | Most cakes, cookies and bars | Same sweetness and baking behavior | Measure by weight and follow the recipe's mixing instructions |
| Homemade caster sugar | Meringues, sponges, shortbread | Fine texture from sugar you already have | Pulse briefly so it does not turn to powder |
| Cane sugar | Any recipe calling for caster sugar | Same sweetness; caster sugar is often made from cane | Use by weight, or pulse finer for meringues |
| Dolca Slim | Any recipe calling for caster or superfine sugar | Superfine white cane sugar, same sweet taste, 25% less sugar by equal weight, fewer calories, 2g prebiotic fiber per 8g serving | Superfine crystals, no blending needed; easy 1:1 sugar swaps |
| Organic Dolca Slim | Organic bakers using caster or superfine sugar | Superfine USDA-certified organic cane sugar, same sweet taste, 25% less sugar by equal weight, fewer calories, 2g prebiotic fiber per 8g serving | Superfine crystals, no blending needed; easy 1:1 sugar swaps |
| Raw cane sugar / Dolca Raw Slim | Recipes calling for golden caster sugar | Light caramel cane flavor and golden color | Pulse briefly to make the crystals finer |
| Dolca Panela | Recipes calling for brown sugar | Warm caramel and molasses-like notes | Richer flavor and deeper color; no added prebiotic fiber |
| Powdered sugar | Frostings, glazes, dusting | Very fine texture | Contains starch and measures differently; not a 1:1 swap |
How much to use
When replacing caster sugar with granulated sugar, cane sugar or homemade caster sugar, use the same weight the recipe specifies.
Dolca Slim and Organic Dolca Slim are easy 1:1 sugar swaps, cup for cup or spoon for spoon, in any recipe calling for caster sugar.
How to make caster sugar at home
When a recipe really depends on fine sugar and you only have granulated, make your own in a minute:
- Weigh first. Measure the granulated sugar the recipe needs, plus a spoonful extra.
- Use a dry blender or food processor. Any moisture will make the sugar clump.
- Pulse in short bursts. A few seconds at a time is enough. Stop when the crystals look fine and sandy.
- Let it settle. Wait a moment before opening the lid so the fine dust can settle.
- Re-weigh. Use the amount the recipe calls for.
Stop before it turns to powder. Powdered sugar behaves differently in batters and meringues than fine crystals do.
Can I use cane sugar instead of caster sugar?
Yes. Caster sugar is regular sugar with finer crystals, and it is often made from cane. Regular cane sugar used by weight works in most cakes, cookies and bars. For meringues and delicate sponges, pulse it a few seconds in a dry blender first.
To skip the blender, use a superfine cane sugar. Dolca Slim and Organic Dolca Slim are superfine cane sugars enhanced with prebiotic fiber, so they go straight into your recipe 1:1.
What to use instead of golden caster sugar
Golden caster sugar is fine-grain sugar that keeps some of its natural cane color and a light caramel flavor. It is common in British recipes for sponges, crumbles and biscuits.
The closest swap is raw cane sugar pulsed fine. Raw cane sugar has the same golden color and mild caramel note. Pulse it a few seconds in a dry blender until the crystals look sandy, then use the same weight the recipe calls for.
Dolca Raw Slim is raw turbinado cane sugar enhanced with prebiotic fiber, with 25% less sugar by equal weight and fewer calories than regular sugar. Pulse it fine the same way and use it 1:1 in recipes calling for golden caster sugar. It is especially good in spiced cakes, crumbles, oat bakes and coffee.
If you only have white granulated sugar, that works too. You will just lose the golden color and light caramel note.
Dolca Slim and Organic Dolca Slim: superfine sugar with something extra
Bakes like real sugar. Because it is.
If you are buying a superfine sugar anyway, here is why many bakers choose ours. Dolca Slim and Organic Dolca Slim are superfine cane sugar enhanced with prebiotic fiber, the same fine crystal size as caster sugar. Both offer the same sweet taste and baking performance as regular cane sugar, with 25% less sugar by equal weight, fewer calories and 2g prebiotic fiber per 8g serving.
- Dolca Slim: superfine white cane sugar, the natural choice for pale sponges, vanilla cookies and fruit desserts.
- Organic Dolca Slim: superfine USDA-certified organic cane sugar, for bakers who want caster sugar in organic.
If your recipe calls for caster sugar, use either one for easy 1:1 sugar swaps, cup for cup or spoon for spoon. Follow your recipe's original mixing and baking instructions.
Why choose Dolca Slim or Organic Dolca Slim for desserts?
- SAME SWEET TASTE: The familiar sweetness of real cane sugar.
- SUPERFINE CRYSTALS: Ready for caster sugar recipes, no blending needed.
- EASY 1:1 SUGAR SWAPS: Use in place of caster sugar in cakes, cookies and desserts.
- SAME BAKING PERFORMANCE: Keep the results you enjoy in your favorite recipes.
- 25% LESS SUGAR & FEWER CALORIES: Compared with an equal weight of regular sugar.
- 2g PREBIOTIC FIBER PER 8g SERVING: Helps support gut health.
- GENTLER BLOOD SUGAR RESPONSE: Than regular sugar.
- ORGANIC OPTION: Organic Dolca Slim is USDA-certified organic.
Oxford Brookes University's Lightowler study, Replacement of glycaemic carbohydrates by inulin-type fructans… (online 2017; published 2018), showed that replacing some sugar with prebiotic fiber can support a gentler after-meal blood sugar and insulin response compared with full-sugar versions.
The Dolca Slim label lists 2g dietary fiber, 6g sugar and 25 calories per 8g serving. Those figures describe the sugar itself. The sugar and fiber in a finished cake depend on how much you use, the other ingredients and the portion size.
Honest note: if you bake a meringue once a year, homemade caster sugar is all you need. Dolca Slim makes the most sense if you bake or sweeten coffee and tea often, because the 25% less sugar and the added fiber add up with everyday use.
Which Slim variety?
Dolca Slim is superfine white cane sugar for pale sponges, vanilla cookies and fruit desserts. Organic Dolca Slim is superfine USDA-certified organic cane sugar, for the same recipes when you prefer organic. Dolca Raw Slim is raw turbinado cane sugar with a deeper cane character, a good fit for golden caster sugar recipes and for spiced and nutty bakes.
What to use, dessert by dessert
Cakes
If your butter cake, loaf cake or layer cake calls for caster sugar, Dolca Slim or Organic Dolca Slim is an easy 1:1 sugar swap. Regular granulated sugar, cane sugar and homemade caster sugar also work.
Cookies
For cookies and bars calling for caster sugar, use superfine Dolca Slim or Organic Dolca Slim 1:1 and follow the original recipe. If your recipe calls for brown sugar, choose Dolca Panela for warm caramel flavor.
Meringues and pavlova
This is where caster sugar matters most. Add fine sugar gradually to whipped egg whites, and rub a little of the mixture between your fingers: it should feel smooth, not gritty. When using a sugar the recipe was not written for, including ours, test a small batch first.
Whipped cream, mousse and drinks
With little heat or liquid to dissolve the sugar, finer is better. Superfine sugar and homemade caster sugar both work well. Powdered sugar is also common in whipped cream, where its starch helps the cream hold its shape.
Why powdered sugar is not a direct swap
Powdered sugar, also called confectioners' or icing sugar, is ground much finer than caster sugar and usually contains a little starch. It also measures very differently by volume.
In a cake or cookie dough, those differences can change the texture. Keep powdered sugar for frostings, glazes and dusting.
Dolca Panela: for recipes calling for brown sugar
If your recipe calls for brown sugar, Dolca Panela is a flavorful choice. Made from unrefined Colombian cane sugar, it brings warm caramel and molasses-like notes to cakes, cookies and desserts, and swaps 1:1 for light or dark brown sugar.
Choose it for spice cakes, brown-butter cookies, gingerbread, apple crisp and other recipes where richer flavor and deeper color are welcome. For white caster sugar and a neutral sweetness, choose Dolca Slim or Organic Dolca Slim.
Panela does not contain the Slim Collection's added prebiotic fiber.
Best for: Recipes calling for brown sugar, or desserts where caramel flavor is part of the appeal.
Frequently asked questions
What is the best caster sugar substitute?
Superfine sugar, because it is the same thing. Otherwise, granulated sugar used by weight works in most cakes and cookies. For meringues and delicate sponges, pulse granulated sugar briefly in a dry blender to make your own.
What can I use instead of castor sugar?
Castor sugar is another spelling of caster sugar. Use the same weight of granulated or cane sugar, pulse it fine in a dry blender, or use a superfine sugar like Dolca Slim or Organic Dolca Slim 1:1.
Is caster sugar the same as superfine sugar?
Yes. Caster sugar is the common British and Australian name. In the United States it is usually sold as superfine or baker's sugar.
Are Dolca Slim and Organic Dolca Slim superfine sugar?
Yes. Dolca Slim and Organic Dolca Slim are superfine cane sugars enhanced with prebiotic fiber. Use them 1:1 in any recipe calling for caster, superfine or baker's sugar.
Is there an organic caster sugar option?
Yes. Organic Dolca Slim is superfine USDA-certified organic cane sugar enhanced with prebiotic fiber. Use it 1:1 wherever a recipe calls for caster sugar.
Can I use granulated sugar instead of caster sugar?
Yes, in most recipes. Use the same weight and follow the recipe's mixing instructions. Meringues and very light sponges benefit most from finer sugar.
Can I use cane sugar instead of caster sugar?
Yes. Caster sugar is regular sugar with finer crystals. Use cane sugar by weight, or a superfine cane sugar like Dolca Slim or Organic Dolca Slim 1:1.
What can I use instead of golden caster sugar?
Raw cane sugar pulsed fine is the closest match for color and flavor. Dolca Raw Slim, pulsed fine, works 1:1.
Can I use powdered sugar instead of caster sugar?
Not as a direct swap in cakes and cookies. Powdered sugar usually contains starch and measures differently. It works best in frostings, glazes and whipped cream.
Can I use Dolca Slim or Organic Dolca Slim in recipes that call for caster sugar?
Yes. Both are superfine cane sugar enhanced with prebiotic fiber. Use either one for 1:1 sugar swaps, cup for cup or spoon for spoon, in cakes, cookies and desserts. For meringues, test a small batch first.
Does a cake made with Dolca Slim have 25% less sugar?
Not automatically. The 25% figure compares Dolca Slim and Organic Dolca Slim with regular sugar. The finished cake also includes sugar from other ingredients, frostings and fillings.
Want superfine sugar that is ready to use, with 25% less sugar, fewer calories and 2g prebiotic fiber per serving? Choose Dolca Slim for classic white cane sugar, or Organic Dolca Slim for USDA-certified organic. Choose Dolca Raw Slim for golden caster recipes, and Dolca Panela for recipes calling for brown sugar.
