Fat loss comes down to eating less energy than you burn. The number that puts you there is easier to estimate than most people think.
The starting formula
Multiply your body weight in pounds by 12–14. That's a reasonable daily calorie target for slow, sustainable fat loss for most adults. A 180 lb person starts around 2,160–2,520 calories. Track it honestly for two full weeks before adjusting.
Protein first
Hit ~0.8 g of protein per lb of body weight (roughly 145 g for a 180 lb person). Protein preserves muscle, controls hunger, and has a higher thermic effect than carbs or fat.
When to adjust
Weigh yourself daily and track the 7-day average. If it hasn't dropped in 10–14 days, cut 100–150 calories or add 1,000 steps per day. Don't slash — nudge.