How Many Calories Are Needed to Lose Weight? | The 600 Rule

Most people looking for weight loss numbers expect a one-size-fits-all answer. A single calorie target that works no matter your age, size, or how much you move.

The real answer depends on you. Weight loss happens when you eat fewer calories than you burn — your Total Daily Energy Expenditure (TDEE). Creating a deficit of 500 to 1,000 calories per day is the standard recommendation for losing 1 to 2 pounds per week at a safe rate, as both Harvard Health and the NHS note. This guide helps you find your personal starting point.

Understanding Your Personal Calorie Needs

Your TDEE is the sum of your basal metabolic rate (BMR) — the energy needed for basic functions at rest — plus the calories you burn through activity. BMR usually accounts for 60 to 75 percent of your daily burn, depending on your muscle mass and body size.

The Mifflin-St Jeor equation is the default formula many calculators use to estimate BMR. It factors in age, sex, height, and weight. If you know your body fat percentage, the Katch-McArdle formula can be more precise because it uses lean mass.

Once you have your TDEE, subtract a calorie deficit to set your weight loss target. Most authorities recommend subtracting 500 to 1,000 calories for a loss of 1 to 2 pounds per week. Individual needs vary, so adjustments based on your response are expected.

Why The “1,200 Calories” Myth Sticks

Many diet articles suggest women eat 1,200 calories and men eat 1,500 calories. Those numbers are the recommended floor — not a target. Eating below these levels without medical supervision can deprive your body of essential nutrients and may slow your metabolism.

• The minimum is not a goal: Harvard Health notes that calorie intake should generally not fall below 1,200 per day for women or 1,500 for men unless under medical supervision. These floors are meant to prevent nutrient deficiencies, not to accelerate weight loss.
• Cutting too low backfires: Severely restricting calories can cause muscle loss, fatigue, and a decline in resting metabolic rate, which makes it harder to keep weight off long-term.
• One size does not fit all: A 6’2″ active man burns far more than a 5’4″ sedentary woman. Using a generic target like 1,200 calories ignores your real energy needs.
• Quality matters as much as quantity: Two people eating the same number of calories can have different body composition changes depending on protein, fiber, and nutrient density of their food.

Instead of adopting a one-size-fits-all number, calculate your own TDEE and subtract a modest deficit. That personalized approach is more sustainable and less likely to cause the metabolic slowdown that often accompanies drastic cuts.

How Many Calories Are Needed to Lose Weight Safely

The most commonly cited safe rate is 1 to 2 pounds per week. To achieve that, you need a daily deficit of 500 to 1,000 calories. The NHS offers a more specific target for the average person: a reduction of about 600 calories from your maintenance level. You can start from the reduce daily intake by 600 guidance if you prefer a single number.

Keep in mind that the 3,500-calorie rule — one pound of fat equals roughly 3,500 calories — is a simplification. Individual metabolism adapts as you lose weight, so your deficit may need to be adjusted over time. What works for the first month may not work for the third.

For most people, a deficit of 500 to 1,000 calories per day is safe and effective. The American Cancer Society also endorses a 500-calorie-per-day deficit as a standard starting point. Combining dietary changes with increased physical activity helps you reach that daily gap without dropping below minimum intake levels.

Daily Calorie Deficit	Approx. Time to Lose 1 lb	Example: Target from 2,000 kcal TDEE
200 kcal	~17.5 days	1,800 kcal/day
300 kcal	~11.7 days	1,700 kcal/day
500 kcal	~7 days	1,500 kcal/day
600 kcal	~5.8 days	1,400 kcal/day
1,000 kcal	~3.5 days	1,000 kcal/day*

*Note: A 1,000 kcal deficit often requires exercise to stay above minimum intake thresholds. Deficits of 200–300 kcal may be too slow for some, but they can still lead to gradual loss. The key is consistency over time.

How to Calculate Your Target Calories

Finding your personal number takes a few simple calculations. You can use an online TDEE calculator or do the math yourself with these steps.

1. Estimate your BMR. Use the Mifflin-St Jeor equation: For women, BMR = (10 × weight in kg) + (6.25 × height in cm) – (5 × age) – 161. For men, substitute +5 for the final constant.
2. Multiply by an activity factor. Sedentary (little exercise): BMR × 1.2; Lightly active (1–3 days/week): BMR × 1.375; Moderately active (3–5 days): × 1.55; Very active (6–7 days): × 1.725; Extra active (hard labor or training twice daily): × 1.9.
3. Subtract your deficit. For weight loss, subtract 500 to 1,000 calories from your TDEE. If you prefer a more modest start, subtract 300 to 500. Ensure your final number is not below 1,200 (women) or 1,500 (men) without medical supervision.
4. Track and adjust. After two weeks of consistent eating at your target, reassess. If you’re losing more than 2 pounds per week or feeling fatigued, increase calories slightly. If you’re losing less, consider a slightly larger deficit or more activity.

These steps give you a starting target. Because metabolism adapts as you lose weight, you may need to recalculate every 10 to 15 pounds lost. A dietitian or healthcare provider can help refine the numbers if progress stalls.

The Role of Exercise and Diet in Your Deficit

A calorie deficit can come from eating less, moving more, or both. The most sustainable approach typically combines moderate dietary reductions with increased physical activity. This allows you to reach a meaningful deficit without cutting food intake to an uncomfortable level.

For example, if you create a 500-calorie deficit through diet alone, you might feel hungry. But if you eat 250 fewer calories and burn an extra 250 through walking or other exercise, the deficit is the same while leaving more food on the plate. Healthline’s calorie limits for weight loss article explores this balance and how it affects sustainability.

Exercise also helps preserve muscle mass during weight loss, which supports a healthy metabolic rate. Resistance training in particular can offset the muscle loss that often accompanies calorie restriction. Even if exercise doesn’t dramatically increase your deficit on paper, its metabolic and health benefits make it a valuable companion to any diet plan.

Method	Typical Calorie Deficit Contributed	Considerations
Dietary reduction alone	300–600 kcal/day	Easier to control but may lead to hunger or nutrient gaps if not planned well.
Exercise alone	200–400 kcal/day (depending on duration and intensity)	Requires consistency and decent fitness level; can be supplemented with diet adjustments.
Combined approach	500–1,000 kcal/day	Most sustainable for most people; allows flexibility and supports muscle preservation.

The Bottom Line

The number of calories needed to lose weight isn’t a universal figure. It depends on your TDEE, activity level, and body composition. A deficit of 500 to 1,000 calories per day is the standard range for safe, sustainable loss of 1 to 2 pounds per week. Start by calculating your personal TDEE, then subtract a modest deficit that keeps you above minimum intake thresholds.

For a more tailored plan that accounts for your specific health status, age, and activity, consider working with a registered dietitian or using a validated online calculator that adjusts as you progress.