To lose weight, eat about 300-500 calories below your maintenance level, or total daily energy expenditure (TDEE). Estimate your TDEE with a calculator or a simple body-weight multiplier, then adjust based on your actual weekly weight trend over two to three weeks. For most people, that means losing roughly 0.5-1% of body weight per week while eating enough protein and lifting weights to protect muscle. There is no single magic number. The right target depends on your size, activity, and body composition. Calculators give a starting point, and your scale trend tells you the truth.
Research in the American Journal of Clinical Nutrition shows moderate deficits produce better long-term results than aggressive restriction. Severe deficits increase hunger hormones, reduce spontaneous movement, and accelerate muscle loss, which is why crash diets so often end in regain. A smaller deficit keeps energy and training quality up while fat comes off steadily.
What TDEE Actually Measures
TDEE is the total number of calories you burn in a day. It has four parts:
- Basal metabolic rate (BMR): the energy needed to keep you alive at rest — breathing, circulation, and cell repair. It is typically 60-70% of TDEE.
- Non-exercise activity (NEAT): walking, standing, fidgeting, chores. This varies enormously between people and often drops when you diet.
- Exercise: planned workouts, usually a smaller share than people expect.
- Thermic effect of food: the energy used to digest food, about 10% of intake and higher for protein.
Eat the same number of calories as your TDEE and your weight holds steady. Eat less and your body draws on stored fat. That deficit can come from eating less, moving more, or both, and combining the two is usually the easiest to sustain.
Step 1: Estimate Your Maintenance Calories
The Quick Multiplier Method
Multiply your body weight in pounds by an activity factor:
- Sedentary (desk job, little exercise): 12-13
- Lightly active (exercise 1-3 days a week): 13-14
- Moderately active (exercise 3-5 days a week plus a fairly active day): 14-16
- Highly active (hard training most days or a physical job): 16-18
A 180-pound person who trains consistently most days lands at roughly 2,520-2,880 calories. Your true maintenance may be a few hundred calories higher or lower depending on genetics, muscle mass, and past dieting, which is fine — you will adjust based on results.
The Calculator Method
Most online TDEE and calorie deficit calculators use the Mifflin-St Jeor equation to estimate BMR, then multiply by an activity factor.
- Men: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
- Women: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
The activity multipliers are 1.2 for sedentary, 1.375 for lightly active, 1.55 for moderately active, 1.725 for highly active, and 1.9 for athlete-level activity. Free tools such as TDEECalculator.net do the math for you.
Worked example: a 35-year-old woman who is 5’6″ and 165 pounds has a BMR of about 1,460 calories. Lightly active, her TDEE is roughly 2,000 calories. A 20% deficit puts her near 1,600 calories a day as a starting target.
Pick Your Activity Level Honestly
This is where most calculators go wrong, because people overestimate activity. Training five days a week while sitting at a desk the rest of the day usually makes you lightly active, not highly active. “Moderately active” means on your feet much of the day and training regularly. “Highly active” is for physical jobs plus hard training. When in doubt, choose the lower category. Starting too high means your “deficit” may actually be maintenance.
Step 2: Set Your Calorie Deficit
Subtract 300-500 calories from maintenance, or about 15-25%. For the moderately active 180-pound example with maintenance near 2,700 calories, that means eating about 2,200-2,400 a day. Expect roughly half a pound to a pound of fat loss per week — the range that preserves muscle best.
Leaner people should use smaller deficits. Men under about 15% body fat or women under about 25% do better near the low end, while people with more fat to lose can handle the high end. Avoid cutting 1,000 calories or more without medical supervision. Most women should not go below about 1,200 calories and most men below about 1,500, since intakes that low make it hard to get enough protein and nutrients.
A Real-Life Example
Bob is a 40-year-old programmer, 5’9″ and 185 pounds, who does not exercise. His estimated TDEE is about 2,090 calories. He wants to reach 165 pounds, which would bring his BMI from about 27 into the healthy range. A 500-calorie daily deficit would take roughly five months, though real-world loss usually slows over time as the body adapts.
Bob has three options: eat about 1,590 calories, add an hour of daily cardio, or combine the two. He drinks a lot of soda, so cutting 250 calories is easy, and 30 minutes of daily walking or cycling burns roughly another 250. The combination is the most sustainable, and as his fitness improves he can gradually extend his sessions.
Step 3: Track What You Actually Eat
Eyeballing portions does not work. Research consistently shows people underreport intake by 30-50%. Weigh and log your food for at least two weeks with a kitchen scale and an app such as MyFitnessPal or Cronometer. Count everything — cooking oil, condiments, snacks, and drinks. A free pour of olive oil can easily be 120 calories, and a handful of nuts 200.
Weigh ingredients raw when possible, since cooked weights vary with water content, and log food as you eat it rather than from memory. After two weeks, you may find you eat far more than you estimated. That gap usually explains a stalled scale.
Step 4: Monitor Progress and Adjust
Weigh yourself daily at the same time — after waking and using the bathroom, before eating or drinking — and look at the weekly average rather than single days. Water, sodium, carbs, and digestion swing daily weight by several pounds.
After two weeks, compare weekly averages:
- Losing about 0.5-1% of body weight per week: your target is working; keep going.
- Losing less than about half a pound per week: cut 100-200 calories and test for another two weeks.
- Losing much faster than 1% per week: add 100-200 calories back to protect muscle and energy.
Stick with each target for at least two weeks before changing it. Adjusting every few days based on daily fluctuations makes it impossible to see what works.
Why Your Numbers Change Over Time
As you lose weight, your TDEE falls because a smaller body burns less energy. Your body also adapts: NEAT drops, you fidget less, and hormone changes reduce energy expenditure. This adaptive thermogenesis can lower TDEE by a further 100-300 calories beyond what weight loss alone predicts. Recalculate every 10-15 pounds lost. What worked at 200 pounds will not produce the same results 20 pounds later.
The classic rule that 3,500 calories equals one pound is a useful shortcut, but it overestimates long-term loss because it ignores this adaptation. Expect progress to slow gradually, and treat slowing as normal rather than as failure. Our guide to breaking a weight loss plateau covers what to do next.
Protein and Macros During a Deficit
Calories determine how much weight you lose; protein largely determines whether it is fat or muscle. Aim for 0.7-1 gram of protein per pound of body weight daily, which is 125-180 grams in our moderately active example. Research in the Journal of Applied Physiology shows higher protein during calorie restriction significantly reduces muscle loss, especially combined with resistance training. Protein also keeps you fuller than carbs or fat.
Fill the remaining calories with carbohydrates and fats based on preference and training. Lifters often perform better with more carbs; others feel better with more fat. As long as protein and total calories are on target, the split is flexible. High-volume, low-calorie foods make the deficit easier; see our list of low-calorie, high-volume foods.
Common Mistakes That Stall Fat Loss
Weekend drift. Tracking carefully Monday to Friday and eyeballing weekends can erase most of the weekly deficit. Your weekly total is what counts.
Liquid calories. Coffee drinks, alcohol, juice, and loaded shakes add hundreds of calories without filling you up. A few weekend drinks can add 500-1,000 calories.
Eating back exercise calories. Fitness trackers and cardio machines often overestimate burn by 20-30% or more. Leave exercise out of your calculations or count only a fraction of it.
Treating calculators as exact. The output is an estimate built on population averages. Your body responds only to actual energy balance, so your scale trend overrides the calculator.
Sustainability Matters More Than Speed
The best calorie target is one you can maintain for months. Aggressive deficits may speed early weight loss, but they increase hunger, sap energy, and rarely last beyond a few weeks. Consider a diet break every 8-12 weeks: one or two weeks at maintenance to ease hunger and fatigue without erasing progress. With a moderate deficit, consistent tracking, and patience, many people lose 20-30 pounds of fat in six to eight months while keeping their muscle and energy.
Frequently Asked Questions
A moderate deficit of a few hundred calories below maintenance produces steady fat loss while protecting muscle and energy.
They are usually within a few hundred calories for most people. Use them as a starting point and adjust based on your weight trend.
Most often, intake is higher than tracked, activity was overestimated, or water retention is masking fat loss.
Generally no, or only a small portion, because trackers tend to overestimate burn.
Every 10-15 pounds lost, or whenever your weekly trend stalls for two to three weeks.
