Royal Icing Calculator

The standard ratio is approximately 500g icing sugar to 2-3 egg whites (about 73ml of pasteurised egg white at the standard 15% egg-white ratio, more if you use larger whites). This produces a thick, stiff icing suitable for piping. For flood icing (a thinner consistency used to fill areas), add water a teaspoon at a time until a ribbon trail holds for about 10 seconds before sinking back. The exact number of whites needed varies slightly by egg size.

For decorating biscuits or cakes that will be eaten by children, pregnant women, or elderly people, use pasteurised egg whites or dried egg white powder (meringue powder) for food safety. Fresh egg whites give a slightly better flavour and whiter colour, and are fine for healthy adults. Pasteurised liquid egg whites from a carton are the most convenient option.

Royal icing has three main consistencies: Stiff peak (for piping flowers and decorations) — the icing stands up straight when you lift the paddle. Soft peak (for outlining and piping lines) — the icing holds briefly then gently falls over. Flood consistency (for filling areas) — thin enough to flow and self-level when you shake the surface. Add water a few drops at a time to thin, or more icing sugar to thicken.

Piped outlines dry to the touch in about 15-30 minutes. Flooded areas take 6-12 hours to dry completely depending on thickness, humidity, and temperature. A thin piped line dries in under an hour. In humid conditions, use a dehumidifier or fan oven on its lowest setting with the door ajar to speed drying. Royal icing on a cake will dry hard in 24-48 hours.

Grainy royal icing is caused by undissolved sugar particles. Always sift the icing sugar thoroughly before mixing — preferably twice through a fine sieve. Beat the icing for at least 5 minutes on medium-high speed to dissolve the sugar fully. If it is still grainy, let the icing rest covered for 30 minutes, then beat again. Using icing sugar from a fresh bag also helps as lumps develop over time.

Use gel or paste food colours, not liquid colours which will thin the icing and change the consistency. Add colour a tiny amount at a time using a toothpick — gel colours are concentrated and a little goes a long way. Note that the colour deepens as the icing dries, so mix to a shade slightly lighter than your target. For dark colours like black or red, colour the icing the day before and let it develop overnight.