Skip to content

Calorie Deficit Calculator

HealthMacros and Calories
About you
Units
Sex
Activity and deficit
Daily calorie target (kcal) —
Resting energy, BMR (kcal)
—
Maintenance calories (kcal)
—
Deficit as share of maintenance
—
Estimated loss per week
—

A calorie deficit is the gap between the energy you burn and the energy you eat. This calculator estimates maintenance with the Mifflin-St Jeor equation and an activity factor, then subtracts your chosen deficit. A 40-year-old woman at 165 cm and 60 kg who is moderately active maintains on about 1,969 kcal, so a 500 kcal deficit gives roughly 1,469 kcal a day.

About this tool

Anyone planning gradual weight loss needs two numbers: how much they burn on an ordinary day, and how far below that to eat. This calculator estimates resting energy from sex, age, height and weight using the Mifflin-St Jeor equation, multiplies it by an activity factor to get maintenance calories, and subtracts the daily deficit you set on the slider. It reports the intake target, the deficit as a share of maintenance and a rough weekly loss using 7,700 kcal per kilogram. The figures are population estimates: individual metabolism can differ by 10% or more, and real loss slows as weight falls, so the weekly number describes the first weeks rather than the whole plan.

How to use it

  1. Pick units and sex

    Choose metric or US units, then male or female, which changes the constant in the equation.

  2. Enter age, height and weight

    These set resting energy, shown as BMR in the results.

  3. Set activity and deficit

    Choose the activity level closest to a typical week, then drag the deficit slider or type an exact kcal value.

Examples

Woman, 40, 165 cm, 60 kg, moderately active

Units
Metric (kg, cm)
Sex
Female
Age
40
Height
165
Weight
60
Activity level
Moderate 3–5 (x1.55)
Daily deficit
500

Result Daily calorie target (kcal): 1,469
Resting energy, BMR (kcal): 1,270
Maintenance calories (kcal): 1,969
Deficit as share of maintenance: 25.4%
Estimated loss per week: 0.45 kg

  1. Weight = 60 kg, height = 165 cm, age = 40
  2. BMR = 10 × 60 + 6.25 × 165 − 5 × 40 − 161 = 1270.3 kcal
  3. Maintenance = 1270.3 × 1.55 = 1968.9 kcal
  4. Target = 1968.9 − 500 = 1468.9 kcal a day
  5. Weekly loss ≈ 500 × 7 ÷ 7,700 = 0.45 kg

Resting energy of 1,270 kcal times 1.55 gives about 1,969 kcal to maintain weight; a 500 kcal cut leaves roughly 1,469 kcal a day.

Man, 35, 5 ft 10 in, 200 lb, lightly active

Units
US (lb, ft, in)
Sex
Male
Age
35
Height
5
and
10
Weight
200
Activity level
Light 1–3 days (x1.375)
Daily deficit
500

Result Daily calorie target (kcal): 2,042
Resting energy, BMR (kcal): 1,848
Maintenance calories (kcal): 2,542
Deficit as share of maintenance: 19.7%
Estimated loss per week: 1 lb

  1. Weight = 90.72 kg, height = 177.8 cm, age = 35
  2. BMR = 10 × 90.72 + 6.25 × 177.8 − 5 × 35 + 5 = 1848.4 kcal
  3. Maintenance = 1848.4 × 1.375 = 2541.6 kcal
  4. Target = 2541.6 − 500 = 2041.6 kcal a day
  5. Weekly loss ≈ 500 × 7 ÷ 3,500 = 1 lb

A 500 kcal daily cut adds up to 3,500 kcal a week, the traditional estimate for one pound of body fat.

How it is calculated

Target = (10 × kg + 6.25 × cm − 5 × age + s) × activity − deficit

s
+5 for men, −161 for women
activity
1.2 sedentary up to 1.9 very hard daily exercise
deficit
daily kcal removed from maintenance

Mifflin-St Jeor (1990) predicts resting metabolic rate from body size and age and is the equation many dietitians prefer for adults. Multiplying by an activity factor estimates total daily energy expenditure. Subtracting the deficit gives the intake target. Weekly loss is deficit × 7 divided by 7,700 kcal per kg (3,500 kcal per lb), a rule of thumb that overstates loss over months because expenditure drops as weight falls.

Sources

When not to use it

  • During pregnancy or breastfeeding, when energy needs rise and a deficit is not advised without clinical input.
  • For people with an eating disorder history, diabetes on medication or other conditions where intake is managed clinically.
  • For teenagers, whose energy needs include growth and are not covered by this adult equation.

Common mistakes

  • Choosing a higher activity level than a typical week supports, which inflates maintenance by hundreds of calories.
  • Expecting the weekly loss figure to hold for months, when expenditure falls as body weight drops.
  • Not recalculating after losing several kilograms, so the target drifts closer to maintenance.

Frequently asked questions

How big should a calorie deficit be?

Many weight-management programmes use 500 to 750 kcal a day, which is often 15 to 25 percent of maintenance for an adult. The share is shown in the results so you can see how aggressive a given number is for your size.

Why does the 3,500 calorie rule overestimate loss?

It treats every pound lost as pure fat and assumes expenditure stays constant. In practice some lean tissue and water are lost, and resting energy falls as weight drops, so loss over months is slower than the rule predicts.

Why is the Mifflin-St Jeor equation used instead of Harris-Benedict?

Comparisons in adults found Mifflin-St Jeor predicted measured resting energy within 10 percent more often than the older Harris-Benedict equation, especially in people with higher body weight.

What does the warning about 1,200 or 1,500 kcal mean?

Those values are widely used lower limits for self-directed diets for women and men. Going lower makes it hard to meet protein and micronutrient needs, so very low intakes are usually supervised.

Does exercise change my target?

Yes, through the activity factor. Moving from sedentary to moderate raises maintenance by about 29 percent, so the same deficit leaves a higher intake target.

Are my measurements sent anywhere?

No. The calculation runs in your browser, and the inputs stay on your device; nothing about your age, height or weight is uploaded.

Cite this tool

Using this tool in an assignment, article or report? Copy a citation, or a link for your website.

APA

Tools Directory Editorial Team. (2026, October 15). Calorie Deficit Calculator. Tools Directory. Retrieved October 25, 2026, from https://tools.milunir.com/health/macros-and-calories/calorie-deficit-calculator/

MLA

Tools Directory Editorial Team. “Calorie Deficit Calculator.” Tools Directory, 15 Oct. 2026, https://tools.milunir.com/health/macros-and-calories/calorie-deficit-calculator/. Accessed 25 Oct. 2026.

Chicago

Tools Directory Editorial Team. “Calorie Deficit Calculator.” Tools Directory. Last modified October 15, 2026. Accessed October 25, 2026. https://tools.milunir.com/health/macros-and-calories/calorie-deficit-calculator/.

Link<a href="https://tools.milunir.com/health/macros-and-calories/calorie-deficit-calculator/">Calorie Deficit Calculator – Tools Directory</a>