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200 to 300 calories less on two to five days beforehand. On the day itself, just enjoy.
Guide · Weekends & exceptions
One day of pizza, cake and wine won't make you gain fat. What the other six days do is what counts.

In short
You balance a cheat day by spreading the extra across several days: 1,500 extra calories means about 300 fewer on five days. What matters is that your week stays in a deficit – not every single day. No starving or punishment workouts needed.
A real feast day is often 1,000 to 2,500 calories above a normal day. With a weekly deficit of 3,500 calories, you're still in a deficit afterwards – just a smaller one. It only becomes a problem if one day regularly wipes out the entire weekly deficit, or one day turns into a whole weekend.
200 to 300 calories less on two to five days beforehand. On the day itself, just enjoy.
Eat a little lighter for a few days afterwards. Calmly, without guilt.
For really big extras like a wedding, spread it over 10 to 14 days.
Work out your extra with the weekend calculator.
The morning after a big meal you often weigh 1–2 kg (2–4 lb) more. That's mostly water: salt and carbs make your body hold fluid, plus the food still in your gut. Gaining a pound of fat would take about 3,500 extra calories. More in why you weigh more after the weekend.
A single bigger meal is usually easier to balance than a whole day. If your cheat day keeps turning into a cheat weekend, one planned favorite meal per week often works better.
As many as your weekly budget allows. With 14,000 a week and 1,800 on the other six days, that's 3,200.
Depends on your deficit. One day a week is usually easy to balance; more than that eats into your deficit fast.
A little less over the next few days is fine. An extreme fasting day isn't necessary.