Fitness · 5 min read
How to Calculate a Calorie Deficit
TDEE minus a planning offset — and why the weekly change is approximate
A calorie deficit is a planning gap between estimated daily energy use (TDEE) and intake. This tutorial walks through Mifflin–St Jeor TDEE, a 500 kcal/day offset, and the ~7700 kcal/kg rule of thumb for weekly change. The result is a screening estimate, not a diet prescription, a guaranteed loss rate, or medical advice.
Written by the My Calculator Stack editorial team. About our methods
This is not medical advice, not a diagnosis, and not a meal plan. TDEE and deficit offsets are coarse planning estimates. The ~7700 kcal per kilogram weekly-change figure is a rule of thumb, labeled approximate — water, glycogen, and adherence change the scale. Talk to a qualified clinician or registered dietitian before changing how you eat, especially if you are pregnant, underweight, or managing a medical condition.
1.What a calorie deficit is
A calorie deficit is intake below estimated daily energy expenditure. On this site, expenditure starts as TDEE: Mifflin–St Jeor BMR times an activity factor. A lose-weight goal on the calorie calculator subtracts about 500 kcal/day from that TDEE. The gap is a planning shift, not a diagnosis of metabolism and not a promise that body mass will fall at a fixed rate. If you want the TDEE piece by itself, see the TDEE tutorial first.
2.The formula
Target intake ≈ TDEE − deficit. TDEE = BMR × activity. Male BMR (Mifflin–St Jeor): 10w + 6.25h − 5a + 5, with w in kg, h in cm, a in years. Female BMR uses −161 in place of +5. Activity factors: sedentary 1.2, light 1.375, moderate 1.55, active 1.725, very active 1.9. A common planning offset is 250–750 kcal/day; this site’s lose-weight goal uses about 500. Weekly mass change is estimated with ~7700 kcal ≈ 1 kg (about 3500 kcal ≈ 1 lb). That ratio is approximate — not a clinical energy balance.
\[ \begin{aligned}\mathrm{target} &= \mathrm{TDEE} - \Delta \\\Delta m &\approx \frac{7\Delta}{7700}\ \mathrm{kg/week}\end{aligned} \]
3.Worked example
Take a metric male, 70 kg, 175 cm, age 30, moderate activity — the same defaults as the calorie calculator. BMR = 10×70 + 6.25×175 − 5×30 + 5 = 1648.75 kcal/day. TDEE = 1648.75 × 1.55 = 2555.5625 ≈ 2556 kcal/day. A 500 kcal/day deficit gives a target of about 2056 kcal/day. Weekly energy gap = 500 × 7 = 3500 kcal, so 3500 / 7700 ≈ 0.45 kg/week. That 0.45 kg is a rule-of-thumb sketch, not a guaranteed weekly change.
\[ 3500/7700\approx 0.45\ \mathrm{kg/week} \]
4.Deficit playground
Switch Metric/US and male/female, then move weight, height, age, and activity to see TDEE update. Drag the deficit slider to subtract from that TDEE. The weekly change uses the ~7700 kcal/kg (or ~3500 kcal/lb) rule of thumb and is labeled approximate. This is a teaching widget — no favorites, no full calculator chrome. Open the calorie calculator when you want goal offsets and the standalone tool.
Inline playground
Activity factor
Target intake
2056 kcal/day
TDEE 2556 kcal/day − deficit 500
Weekly change (approximate, ~7700 kcal/kg): ≈ 0.45 kg
2556 − 500 = 2056
Screening aid only — not medical advice, not a diagnosis. The ~7700 kcal/kg weekly figure is a rule of thumb, labeled approximate.
5.Open the full calculator
The calorie calculator uses the same Mifflin–St Jeor BMR, the same activity factors, and the same 70 kg / 175 cm / age 30 example, with How it works, FAQ, and related fitness tools on one page. Browse the TDEE and BMR tutorials if you want the resting and daily-energy pieces next.
Try it yourself
Open the related calculator and put these formulas to work.