How much yeast for 40 pints of beer?

How Much Yeast Do You Need for 40 Pints of Beer?

When brewing 40 pints—roughly 23 litres—of beer, one of the most common questions homebrewers ask is, how much yeast should I use? The general rule of thumb is to use between 5 and 10 grams of dried yeast, depending on the strain and fermentation conditions.

This range works well when your wort is held at a steady 16 to 22 degrees Celsius during fermentation. Yeast thrives in this temperature window, ensuring a healthy, active fermentation that brings out the best in your brew. However, if you're fermenting at a cooler temperature—say, for a lager or a crisp ale—consider leaning toward the higher end of that range, or even slightly above. Cooler temps slow yeast activity, so a bit of extra yeast helps ensure a strong, reliable start.

Many brewers find it tempting to just sprinkle dry yeast directly onto the wort—what’s known as “sprinkle pitching.” While this method can work, there’s a better way. Rehydrating your yeast first can significantly improve viability and performance. Simply stir the yeast into a small amount of warm (not hot) water about 15–20 minutes before pitching. This wakes up the yeast cells gently, giving your fermentation a faster, more consistent start.

Of course, always check the manufacturer’s instructions—some modern yeast strains are designed to be pitched directly. But if you’re aiming for consistency and control, especially with bigger batches, rehydration and proper dosing make a noticeable difference. Whether you're brewing a hoppy pale ale or a smooth stout, getting the yeast right is one of the simplest ways to elevate your beer.