How to Calculate a Calorie Deficit for Weight Loss, Step by Step

Here is how to calculate a calorie deficit: estimate how many calories your body burns in a day (your maintenance calories, or TDEE), then subtract a moderate amount, commonly around 300 to 500 calories, to get a daily target. Track what you eat against that target for a few weeks and adjust based on how your weight actually changes.

That is the whole method. The rest of this guide walks through each step with a worked example, plus the common mistakes that make a deficit stop working.

What a calorie deficit is and how to calculate it

A calorie deficit simply means eating fewer calories than your body uses. When that happens consistently, your body makes up the difference from stored energy, and over time your weight goes down.

Your daily calorie burn has a few parts:

• Basal metabolic rate (BMR): the energy your body uses at rest to breathe, circulate blood, and keep organs running. This is usually the largest part.
• Activity: everything from walking to the kitchen to a structured workout.
• Digesting food: a smaller share of energy goes into processing what you eat.

Together, these make up your total daily energy expenditure, or TDEE. Your deficit is measured against that number.

Step 1: Estimate your BMR

The Mifflin-St Jeor equation is one of the most widely used formulas for estimating BMR:

• Men: (10 x weight in kg) + (6.25 x height in cm) - (5 x age) + 5
• Women: (10 x weight in kg) + (6.25 x height in cm) - (5 x age) - 161

Example: a 35-year-old woman who weighs 80 kg and is 165 cm tall.

• 10 x 80 = 800
• 6.25 x 165 = 1,031
• 5 x 35 = 175
• 800 + 1,031 - 175 - 161 = about 1,495 calories

This is an estimate. Real metabolic rates vary from person to person, which is why step 5 matters.

Step 2: Multiply by an activity factor to get TDEE

Multiply your BMR by the factor that best matches your typical week:

Our example woman walks a few times a week and has an office job, so "lightly active" fits: 1,495 x 1.375 = about 2,055 calories per day. That is her estimated maintenance level.

Tip: Most people overestimate their activity. If you are unsure between two levels, pick the lower one.

Step 3: Choose a sensible deficit size

A commonly recommended approach is a daily deficit of roughly 300 to 500 calories. The traditional rule of thumb says that about 3,500 calories equals one pound of body fat, so a 500-calorie daily deficit has long been linked to losing around a pound a week. In reality, weight loss tends to slow over time as your body adapts, so treat that as a rough starting expectation rather than a promise.

When choosing your deficit, consider:

• Smaller deficits are easier to sustain. You will feel less hungry and keep more energy for daily life and workouts.
• Larger deficits are harder to stick to and can make it difficult to get enough protein and nutrients.
• Very low intake needs supervision. Many health sources suggest not going below about 1,200 calories a day for women or 1,500 for men without guidance from a doctor or dietitian.

For our example, a 400-calorie deficit gives a daily target of about 1,650 calories.

Step 4: Turn the target into daily meals

A number is only useful if you can eat to it. Split your target into rough meal budgets so it feels manageable:

• Breakfast: about 350 calories
• Lunch: about 450 calories
• Dinner: about 550 calories
• Snacks: about 300 calories

These do not need to be exact. They are guardrails that stop you from arriving at dinner with almost nothing left. Prioritizing protein and fiber at each meal helps you feel full on fewer calories; our list of high-protein foods for weight loss has practical options.

Then log what you eat. A food photo app such as NutriVision makes this quick: snap your meal, review the estimated calories and macros, and see how much of your personal calorie target is left for the day.

Step 5: Check your progress and adjust

Formulas get you a starting point, but your scale and food log tell you the truth. Here is how to calibrate:

1. Track for two to four weeks. Day-to-day weight jumps around because of water, salt, and digestion. You need several weeks of data.
2. Look at the trend, not single weigh-ins. Weekly averages are much more reliable than any one morning.
3. If weight is dropping at a comfortable pace, keep going.
4. If weight is not moving, first check your logging. Are oils, drinks, and weekend meals included? If logging is solid, reduce your target by around 100 to 200 calories.
5. If you are losing quickly and feel drained, add some calories back. Fast loss is not automatically better.
6. Recalculate after meaningful weight loss. A smaller body burns fewer calories, so your maintenance number drops as you lose weight.

Common calorie deficit mistakes

• Counting exercise calories twice. If you used an "active" multiplier, do not also eat back every calorie your watch says you burned.
• Only tracking weekdays. Two unlogged weekend days can erase a week of careful eating.
• Cutting too hard, too fast. Aggressive deficits often lead to rebound eating.
• Ignoring protein. Adequate protein helps preserve muscle while you lose fat.
• Expecting a straight line. Plateaus and water-weight swings are normal. If you stall for several weeks, read our guide on breaking a weight loss plateau.

Frequently asked questions

How many calories should I cut to lose weight?

A deficit of roughly 300 to 500 calories below your maintenance level is a common, sustainable starting point for most adults. Your ideal number depends on your size, activity, and health, so check with a professional if you are unsure.

Is a 1,000-calorie deficit safe?

A deficit that large can be hard to sustain and may leave your intake too low to meet nutritional needs. Large deficits are best attempted only with guidance from a doctor or registered dietitian.

Why am I not losing weight in a calorie deficit?

The most common reasons are underestimated food intake, overestimated activity, and normal water-weight fluctuations hiding fat loss. Track carefully for a few more weeks and adjust your target if the trend stays flat.

Do I need to recalculate my calorie deficit?

Yes. As you lose weight, your maintenance calories decrease. Recalculating after every several kilograms or pounds lost keeps your deficit accurate.

NutriVision sets a personal calorie target, logs meals from a photo, and tracks your weight and BMI so you can see whether your deficit is working. Get NutriVision free on Google Play and start tracking your deficit today.