Calorie Deficit Calculator

Calorie deficit calculator for daily calorie targets and weight goals

A calorie deficit is the gap between the calories your body uses (your maintenance calories) and the calories you eat. When you consistently eat below maintenance, your body has to cover some of its energy needs from stored energy, which typically shows up as weight loss over time. This calculator helps you translate a goal into a practical daily calorie target by estimating your maintenance calories and then calculating the deficit needed.

The calculator supports two common real world approaches. If you have a specific target weight and a timeframe, it calculates the daily deficit needed to reach that target on average. If you prefer a steady pace, you can set a weekly rate (for example 0.25 kg to 0.75 kg per week) and it will calculate the daily deficit that rate implies. Either way, you also get a quick summary showing how big the deficit is per day and per week, plus what daily calorie intake that suggests.

To make the tool usable even when you do not have perfect data, maintenance calories can be estimated from your age, sex, height, weight, and activity level. If you already know your maintenance calories from a wearable, a food tracking app, or prior tracking, you can enter it as an override and the calculator will use your number instead of the estimate. The results are estimates, not guarantees. Day to day scale changes are noisy, so the useful signal is the trend over multiple weeks.

Assumptions and how to use this calculator

• Maintenance calories are estimated using a standard BMR formula plus an activity multiplier. This is an estimate, not a measurement.
• Energy-to-weight conversion is simplified using 7,700 kcal per kilogram of body weight change. Real outcomes vary by person and over time.
• Weight change is treated as a smooth weekly average. In practice, water, glycogen, digestion, and sleep can mask progress for days.
• If you enter a maintenance calorie override, that value replaces the estimate entirely and will drive the rest of the outputs.
• Very aggressive deficits can be unsafe, especially for teens, athletes, and people with medical conditions. Use conservative targets and seek professional advice if unsure.

Common questions

What is a reasonable calorie deficit?

For many adults, a moderate deficit is often more sustainable than a large one. A common range is around 10% to 25% below maintenance, depending on starting point and goals. If the deficit is too large, hunger, fatigue, poor training performance, and rebound eating become more likely. This calculator flags overly aggressive results so you can adjust your plan.

Why does the calculator ask for sex, height, weight, age, and activity?

Those inputs are used to estimate maintenance calories when you do not provide your own maintenance number. Weight and height influence baseline energy needs, age shifts the estimate slightly, and activity level scales the estimate based on how much energy you likely burn through movement and training. If you already know your maintenance calories, you can skip relying on the estimate by using the override field.

What if I do not know my maintenance calories?

Use the estimate as a starting point. The most practical way to improve accuracy is to track food intake and body weight trend for 2 to 4 weeks. If your weight trend is stable, your average intake is close to maintenance. If you are losing faster than expected, maintenance might be lower than estimated; if you are losing slower, it might be higher. Small adjustments are usually better than large swings.

Why can my scale weight stall even when I am in a deficit?

Short stalls are common. Water retention from stress, salt, training soreness, and hormonal changes can temporarily hide fat loss. The most useful approach is to compare weekly averages rather than single weigh-ins. If your trend is flat for several weeks, then it is time to reassess either your calorie intake, your activity level, or the accuracy of your tracking.

Does this apply to teens or people with special medical situations?

If you are under 18, pregnant, breastfeeding, recovering from an eating disorder, or managing a medical condition, calorie targets can be more complex and the risks of aggressive dieting are higher. Use this calculator only as a rough educational estimate and consult a qualified health professional for personalized guidance. If the suggested intake feels extreme or drives anxiety or compulsive restriction, do not follow it.