Calorie deficit calculator:
set a gap you can actually sustain

What a calorie deficit is

A calorie deficit means that, over time, you eat fewer calories than your body uses. The gap has to be made up from somewhere, and the body draws on stored energy to cover it.

The number your body uses in a day is called total daily energy expenditure, or TDEE. It covers resting needs, movement, exercise and digestion. If you do not know yours, work it out first with the TDEE calculator on this page.

• Intake equal to TDEE is maintenance, and weight tends to hold steady.
• Intake below TDEE is a deficit, and weight tends to drift down.
• Intake above TDEE is a surplus, and weight tends to drift up.

A deficit is a planning tool, not a guarantee. Real-world weight change moves in a jagged line, with water, salt and digestion hiding the trend from day to day.

Calorie deficit formula

The third formula is the one to watch. A 300 kcal gap is modest for someone burning 2,800 kcal and aggressive for someone burning 1,600. Thinking in percentages stops you borrowing a number that was set for a different body.

Worked example: finding a 300 kcal deficit

Take someone whose estimated TDEE is 2,300 kcal a day and who plans to eat 2,000 kcal a day.

The gap does not have to come from food alone. Trimming 200 kcal from meals and adding a daily walk worth about 100 kcal gives the same 300 kcal gap, and may feel easier to keep up.

Looking at a week helps. A 300 kcal daily gap adds up to 300 × 7 = 2,100 kcal across the week, which shows how steady, small gaps do the work and why a single large meal does not undo them.

Walking calories vary with body weight, pace and distance, so treat the 100 kcal as a rough placeholder rather than a measurement.

How big should the deficit be?

A moderate gap is easier to sustain than a deep one. A common rule of thumb is a deficit of about 10% to 20% of TDEE, because hunger, energy and mood tend to suffer less than with large cuts.

Public-health bodies such as the CDC describe a gradual pace, around 1 to 2 pounds (roughly 0.5 to 1 kg) a week, as typical for steady weight loss. Do not expect that on every single week, and do not chase it with a bigger deficit.

As a rough floor, many general guidelines advise against going below about 1,200 kcal a day for women or 1,500 kcal a day for men without medical supervision. Smaller people, older adults and anyone with a health condition should get individual advice rather than rely on a floor.

Turning a deficit into daily choices

A target of 2,000 kcal means little unless it changes what ends up on the plate. Fat carries about 9 kcal per gram and carbohydrate or protein about 4 kcal per gram, which makes some small swaps worth more than they look.

Check labels and measure oil with a spoon for a week. Cooking fat and liquid calories are often the easiest places to find a saving, because they add up without changing what the plate looks like.

1. 1Estimate your TDEE and choose a deficit of a size you can repeat for weeks.
2. 2Convert it into a daily intake figure and spread it across meals you will actually eat.
3. 3Weigh yourself at the same time a few days a week and record the weekly average.
4. 4Review after two to three weeks and change only one thing: intake or movement.

Why a calorie deficit does not always show on the scale

• Weekend drift. A 300 kcal deficit on five weekdays is 1,500 kcal. A 400 kcal surplus on two weekend days takes back 800, leaving a net of 700 kcal a week, or about 100 kcal a day.
• Your TDEE falls as you lose weight. A 5 kg lower body weight reduces the Mifflin-St Jeor estimate by about 50 kcal a day, so a fixed intake slowly becomes a smaller deficit.
• Water and salt. A salty meal, a hard workout or hormonal shifts can add or remove a kilo of water overnight.
• Inaccurate tracking. Oils, snacks and portions are easy to underestimate, and food labels can be off.

Judge progress by a two- to three-week average of weekly weights, waist measurement and how your clothes fit, not by one morning's reading.

Safety limits and when to ask for help

A deficit is not suitable for everyone. Children and teenagers, pregnant or breastfeeding women, people recovering from illness and anyone with a history of disordered eating should not plan their own calorie cuts.

If you have diabetes, a heart condition, thyroid problems or take regular medication, speak to your doctor first. A registered dietitian can build a plan around your health, food preferences and routine.

Plan a break too. After a few months of eating below maintenance, spending a couple of weeks at your estimated TDEE gives your routine, sleep and training a chance to recover, and it tells you whether your maintenance estimate was close.

Stop and seek advice if you feel faint, constantly fatigued, cold, or find yourself obsessing over food. Those are signs the deficit is too big or the approach is not working for you.

Your daily needs and BMR guides on this site cover how the starting numbers are built, if you want to see the steps behind the 2,300 kcal figure.