How Many Calories to Eat to Lose Weight: Deficit Guide

By the Weight Loss 4 Wellness editorial team · Updated November 2, 2026 · How we research

A calorie deficit simply means taking in a little less energy than your body uses, so it draws on stored energy instead. The hard part is not the idea; it is choosing a deficit big enough to work and small enough to live with. Here is how to estimate your number, what clinical guidelines recommend, and why the math gets fuzzier over time.

Key takeaways

Start by estimating your maintenance calories, then eat roughly 500–750 calories a day below it. That is the range used in U.S. obesity treatment guidelines.
Guidelines often use 1,200–1,500 calories a day for women and 1,500–1,800 for men as weight-loss intakes. Going lower should be supervised by a clinician.
Formulas are estimates. Your weight trend over 2–3 weeks tells you more than any calculator.
Weight loss slows as you get lighter, so the old “3,500 calories = 1 pound” rule overpromises.
Losing even 5% of your body weight is linked with meaningful health improvements for many people.

What is a calorie deficit?

Your body burns energy all day: to keep your organs running (your resting or basal metabolic rate), to digest food, and to move. Together that is your total daily energy expenditure, often shortened to TDEE or “maintenance calories.” When you eat fewer calories than that total over weeks, your body makes up the difference from stored energy, mostly fat, and your weight trends down.

No food or supplement gets around this. Different eating styles (low-carb, Mediterranean, intermittent fasting) can make a deficit easier or harder for a given person to stick to, but they work through the same energy balance.

Step 1: Estimate your maintenance calories

The most widely used estimate for adults is the Mifflin-St Jeor equation. It predicts resting burn from weight, height, age and sex, and you multiply it by an activity factor:

Women: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
Men: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5

Multiply the result by about 1.2 if you mostly sit, 1.375 if lightly active, 1.55 if moderately active, or 1.725 if very active. Our free calorie deficit calculator does the arithmetic for you.

Validation research has found Mifflin-St Jeor to be one of the more accurate equations across body sizes, but it is still off by more than 10% for a sizable minority of people. Treat the number as a starting estimate, not a fact about your body.

Step 2: Choose a sensible deficit

The 2013 obesity guideline from the American Heart Association, American College of Cardiology and The Obesity Society describes three common ways clinicians set a reduced-calorie diet:

Approach	What it looks like
Subtract from maintenance	About 500–750 calories a day below your estimated needs
Fixed intake ranges	About 1,200–1,500 calories a day for women and 1,500–1,800 for men, adjusted for body weight
Structured plans	Evidence-based diets or programs that create a deficit by limiting certain foods

The CDC notes that people who lose weight gradually and steadily, roughly 1 to 2 pounds a week, are more likely to keep it off. A bigger deficit is not automatically better: very low-calorie diets can make it hard to get enough protein, fiber and micronutrients, and they are meant to be used only under medical supervision.

Talk to a clinician first if you are pregnant or breastfeeding, take medication for diabetes or blood pressure (doses may need adjusting as you lose weight), have kidney disease, or have a history of disordered eating.

Step 3: Track the trend, then adjust

Daily weight jumps around with water, salt, hormones and digestion. Instead of reacting to single weigh-ins:

Weigh yourself at the same time of day a few times a week and look at the weekly average.
Give any calorie target two to three weeks before judging it.
If the average is not moving and you have been consistent, trim about 100–200 calories a day or add more daily movement, rather than making a big cut.
If you are losing much faster than about 1–2 pounds a week after the first couple of weeks, eat a little more.

Why the “3,500 calories per pound” rule misleads

You may have read that cutting 500 calories a day always equals a pound a week. Researchers have shown this rule overestimates weight loss over months, because a smaller body burns less energy and the deficit shrinks as you go. The NIH’s Body Weight Planner uses a dynamic model that accounts for this, and it is a good tool for seeing a realistic timeline. Expect loss to be faster at first (partly water) and slower later. That slowdown is normal, not failure. Our guide to weight loss plateaus covers what to do when it happens.

Making a deficit easier to live with

Lead with protein. It is filling and helps protect muscle while you lose weight. See how much protein you need.
Add volume with fiber. Vegetables, fruit, beans and whole grains fill the plate for relatively few calories.
Watch liquid calories. Sugary drinks, specialty coffees and alcohol add up without filling you up.
Move more in ordinary ways. Daily steps raise your burn without making you as hungry as hard workouts can. Our walking guide explains how much helps.
Protect your sleep. Short sleep tends to make hunger and cravings harder to manage.

How much weight loss is worth it?

Health benefits do not start only at a “goal weight.” Guidelines note that sustained loss of about 3–5% of body weight can improve blood sugar and blood fats, and larger losses bring further benefits. For a 200-pound person, 5% is 10 pounds. That is a goal you can reach and keep.

Frequently asked questions

Should I eat back the calories I burn exercising?

Usually not all of them. Fitness trackers often overestimate exercise burn, and activity is already part of your maintenance estimate if you chose the right activity level. If you are hungry on hard training days, eating back a portion, such as a third to a half, is a reasonable middle ground. Let your weekly weight trend guide you.

Can I lose weight without exercising?

Yes. A calorie deficit can come from food alone. Exercise still matters: it helps preserve muscle, supports keeping weight off, and improves heart health and mood. The Physical Activity Guidelines recommend at least 150 minutes of moderate activity a week plus two days of muscle strengthening for adults.

How long will it take to lose 20 pounds?

At a steady 1 to 2 pounds a week, about 10 to 20 weeks, and often longer, because loss slows as you get lighter. The NIH Body Weight Planner gives a personalized timeline.

What is the lowest number of calories I should eat?

Guidelines commonly use 1,200–1,500 calories a day for women and 1,500–1,800 for men as weight-loss intakes. Eating less than that should be planned and monitored by a doctor or registered dietitian.

How Many Calories Should You Eat to Lose Weight? A Realistic Calorie Deficit Guide