Beer is water, malt, hops and yeast, and making it is four decisions and three measurements. The decisions are what to brew, how warm to mash it, how much to hop it and how warm to ferment it. The measurements are the strike temperature before you start, the gravity before and after fermentation, and the priming weight at packaging. Nearly everything written for beginners covers the decisions in detail and waves at the measurements, which is why so many second batches are a surprise. This runs the day in order and puts each measurement where it belongs.
Before the kettle: water and temperature
Weigh the grain, pick a mash temperature (66°C is a sensible default that gives a beer with some body and still ferments out) and work out the strike temperature, which is not the same thing. The grain arrives at room temperature and steals heat, roughly four tenths of what water takes per kilogram, so a 66°C mash at three litres per kilogram wants water somewhere near 72°C. Get this wrong low and the beer finishes thin; get it wrong high and it finishes sweet and may stall.
Mash, sparge, boil
Hold the mash for an hour, which is comfortably longer than conversion actually needs and costs nothing. Rinse the grain with the sparge water: the total the day needs is what you want in the fermenter plus what the kettle boils off plus what the spent grain keeps, and the grain keeps roughly a litre per kilogram. Boil for an hour with the bittering hops in at the start and the aroma hops near the end, then cool as fast as you can and get it into the fermenter.
The reading that has to happen before the yeast
Fill a trial jar from the fermenter, spin the hydrometer to shed bubbles, read the bottom of the meniscus, and correct to 20°C if the sample is warm. That is the original gravity, and it has to be taken before fermentation starts (HMRC's guide says as soon as possible after filling, normally within the hour) because once the yeast has begun there is no way back to it. Then pitch, seal, and leave it somewhere at a steady temperature.
Finishing, and the two numbers that come out
Wait until two readings two or three days apart agree. Put both readings into the ABV calculator and it gives the strength by HMRC's factor method: 1.048 down to 1.011 is 37 degrees, factor 0.130, 4.8%, rounded down, as duty is. Then prime from the carbon dioxide the beer is already carrying at the warmest temperature it reached, bottle or keg, and leave it two weeks warm. Write down the boil-off, the absorption and the efficiency you actually got, because those are properties of your kit and they make every future recipe land.
How to make lager, and why it is harder
Lager is the same day with a colder, longer ferment and a month of cold conditioning after it. What makes it hard at home is not the recipe, it is temperature control: lager yeast at ale temperatures makes a beer that tastes of ale, so you need a fridge with a controller or a cold garage in February. Fermenting under a little pressure is the common workaround, and it works, but remember it leaves the beer carrying much more dissolved carbon dioxide than an airlocked one before you prime it.
Questions people ask about how to make beer
Do I have to mash, or can I start with extract?
Extract skips the mash entirely and every measurement after it is identical, so it is a perfectly good place to start. Dissolve the extract, boil with hops, cool, pitch. You lose control over the body of the beer and gain about two hours of your Saturday.
How long from brew day to a drinkable pint?
Roughly four weeks for an ale: a day brewing, one to two weeks fermenting, two weeks conditioning in the bottle. Lagers take two to three months. Nothing on that timeline is optional except your patience in the last week.
Why did my beer come out weaker than the recipe said?
Almost always brewhouse efficiency. A recipe written for 75% and brewed at 62% loses roughly a percent of alcohol on an ordinary beer. Put the gravity you actually got into the mash water calculator and it will tell you the efficiency you achieved; use that figure next time and the recipe lands.
Is it legal to brew beer at home in the UK?
Yes, for your own consumption, with no licence and no duty. Selling it brings HMRC's approval and duty regime with it, and distilling at home is not lawful here without a licence: this site has nothing to say about that.
What should the first batch be?
Something ordinary in strength and forgiving in temperature: a pale ale around 1.045 with a clean ale yeast. Strong beers punish a gravity you did not hit, and lagers punish temperature control you probably do not have yet.