How to calculate a calorie deficit for steady weight loss
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A calorie deficit is the foundation of every successful fat loss plan. No matter what diet you follow, they all work through the same mechanism: consuming fewer calories than you burn.
Use the calorie deficit calculator
Calculate maintenance, a planned weekly rate and a daily calorie target.
Open the free calculator →What is a calorie deficit?
A calorie deficit occurs when you eat fewer calories than your body burns in a day (your TDEE). Your body then turns to stored energy — primarily body fat — to make up the difference. Over time, this produces fat loss.
📌 The maths: 1 kg of body fat stores ~7,700 calories. A 500 kcal daily deficit burns through roughly 1 kg of fat every 15 days.
Step 1: Find your TDEE
You need to know how many calories you burn on a typical day before you can create a meaningful deficit.
Find your personalised maintenance calories in 30 seconds.
Calculate my TDEE →Step 2: Choose your deficit size
- Small (200–300 kcal/day): Very sustainable, minimal hunger. Loss ~0.2–0.3 kg/week.
- Moderate (400–500 kcal/day): The sweet spot for most people. Loss ~0.4–0.5 kg/week.
- Larger (500–750 kcal/day): Faster results but harder to sustain long-term.
- Aggressive (750–1000 kcal/day): Only short-term or under medical supervision.
Step 3: Set a calorie floor
Never go below: 1,200 kcal/day for women or 1,500 kcal/day for men without medical supervision. Very low calories risk muscle loss, nutritional deficiencies, and metabolic slowdown.
Why protein matters in a deficit
When you eat less, your body can break down muscle for energy if protein intake is too low. To protect muscle mass, aim for 1.6–2.2g of protein per kg of bodyweight per day. This is the highest-leverage change most people can make alongside their calorie target.
Common mistakes
Underestimating calories eaten
Research shows people underestimate their food intake by 20–40%. Oils, sauces, drinks, and snacks are the most common culprits. Even a few weeks of tracking accurately produces lasting awareness.
Not recalculating as weight drops
As you lose weight, your TDEE decreases. Recalculate every 4–6 weeks or when your weight drops by 3–5 kg. This is why many people hit a plateau — their deficit has silently disappeared.
Key takeaways
- Find your TDEE first, then subtract 300–500 calories for a sustainable deficit.
- Don't go below 1,200 kcal (women) or 1,500 kcal (men) without medical guidance.
- Eat 1.6–2.2g protein per kg of bodyweight to preserve muscle during fat loss.
- Track intake honestly — most people underestimate significantly.
- Recalculate targets every 4–6 weeks as your weight changes.
How to know whether the deficit is working
Use the average of several morning weigh-ins and compare week to week. A single day can move because of sodium, bowel contents, menstrual cycle, travel, heat or a hard workout. Waist measurement and clothing fit provide useful extra context.
If the trend is flat for two to four weeks, verify portions and activity before making a large cut. Small adjustments are easier to assess and maintain.
Avoid an unnecessarily large deficit
More aggressive is not always faster in practice. Very low intake can increase hunger, fatigue and loss of training performance, making adherence worse. The right deficit is one you can sustain while meeting nutrition needs and functioning normally.
A simple way to put this into practice
- Choose one measurable behavior for the next seven days.
- Keep the rest of your routine reasonably stable.
- Review weekly averages rather than one-day results.
- Adjust only after you have enough information.
Sources and evidence base
- National Institute of Diabetes and Digestive and Kidney Diseases — Weight Management
- Centers for Disease Control and Prevention — Healthy Weight and Growth
- Physical Activity Guidelines for Americans
- USDA FoodData Central
References support general principles; they do not make EKCal a substitute for clinical care. See our Editorial Policy and Sources & Methodology.