In the U.S., caster sugar is most commonly labeled as superfine sugar or sometimes baker’s sugar. It has smaller crystals than regular granulated sugar, so it dissolves more quickly in batters, meringues, and even cold drinks.

• Texture: Finer than granulated, coarser than powdered.
• Uses: Helpful for light cakes, crisp cookies, and beverages.
• Where to look: Online, you’ll typically find it in the Baking or Pantry sections. Searching “caster sugar” or “superfine sugar” can help.

If a recipe calls for “caster sugar,” choosing a product labeled “superfine” can offer a similar result, though outcomes can vary by recipe.

A few options can work, depending on your recipe and tools:

• Superfine sugar: If you see sugar labeled “superfine,” it’s a close match.
• DIY from granulated: Pulse regular granulated sugar in a food processor until the crystals are smaller (avoid overprocessing). This can mimic caster sugar, though texture can vary.
• By weight, not volume: If substituting, measuring by weight can help keep sweetness consistent.

For frostings, powdered sugar can be useful, but it usually contains starch and may change texture. If you’re sweetening beverages, simple syrup can dissolve more easily than dry sugar.

You can create a caster-like texture at home with a processor or blender.

1. Add sugar: Place a small batch of granulated sugar in the bowl (about 1 cup).
2. Pulse briefly: Use short pulses, shaking occasionally, until the crystals look like fine sand.
3. Check texture: Stop before it becomes powdery (that leans toward powdered sugar).
4. Let dust settle: Wait a few seconds before opening the lid.
5. Store: Transfer to an airtight container to keep it dry.

This approach can approximate caster sugar for many baking tasks, though exact results may vary by recipe and equipment.

They’re not the same and behave differently in recipes.

• Caster sugar (superfine): Tiny crystals that dissolve quickly. Useful for cakes, cookies, and meringues where a fine texture is helpful.
• Powdered sugar (confectioners’): Ground to a powder and typically blended with a small amount of starch. Great for frostings, glazes, and dusting.

Substituting powdered sugar for caster sugar can change texture and moisture because of its powdery consistency and added starch. If you’re aiming for a similar crystal structure, caster or homemade superfine sugar is usually closer, but outcomes can depend on the specific recipe.

Good storage helps keep caster sugar free-flowing and easy to measure.

• Use an airtight container: Seal out humidity to prevent clumps.
• Keep it cool and dry: A pantry or cupboard away from heat and steam works well.
• Avoid odors: Store away from strongly scented items; sugar can absorb smells.
• If clumps form: Gently break them up with a fork or sift before using.
• Label and date: Helpful for rotation and quick identification.

Sugar is shelf-stable and can last a long time when kept dry. Storage conditions can affect texture, so a tight seal usually helps maintain consistency.