Last updated: 2026-06-29

Calorie Deficit Target

A calorie deficit target calculator works backwards from a goal: you fix the weight you want to reach and the date you want to reach it by, and it returns the daily calorie intake you would need to hold to get there. It is the inverse of a weight-loss timeline, which starts from a chosen deficit and projects how long the goal will take. This tool answers the more common planning question — "what should I eat per day to lose a set amount by a set date?" — by combining an estimate of your maintenance calories with the deficit your deadline implies.

How the daily target is calculated

The calculation has three parts. First it estimates your maintenance calories, or total daily energy expenditure (TDEE) — the intake that holds your weight steady. TDEE is your basal metabolic rate (BMR) multiplied by an activity factor. BMR comes from the Mifflin-St Jeor equation, which is the most widely validated predictive formula for resting metabolism:

where $w$ is weight in kilograms, $h$ is height in centimetres, $a$ is age in years, and $s$ is $+5$ for men and $-161$ for women.

Second, it works out the daily deficit your goal requires. Losing body fat releases energy, and a commonly used approximation is that one kilogram of fat stores about 7,700 kcal (equivalently, 3,500 kcal per pound). Spreading the total energy gap across the available days gives:

Third, the daily target is simply maintenance minus that deficit:

Worked example

Consider a 35-year-old man, 175 cm tall, weighing 82 kg, who is moderately active and wants to reach 74 kg in 14 weeks.

So he would aim for roughly 2,074 kcal per day, a deficit of about 629 kcal below maintenance, implying a loss of about 0.57 kg per week. That rate sits inside the commonly recommended 0.5–1 kg (1–2 lb) per week band, so the plan reads as sustainable.

Why the linear estimate overstates loss

The 7,700-kcal-per-kilogram rule treats the body as a fixed energy account, but metabolism is not static. As weight falls, resting metabolic rate and the energy cost of moving both decline — a response known as adaptive thermogenesis. The real deficit therefore shrinks as the diet progresses, and actual loss plateaus below the straight-line projection. Kevin Hall and colleagues quantified this in work showing why the 3,500-kcal rule systematically overestimates long-term loss. For a dynamic model that accounts for the slowdown, the NIH Body Weight Planner is the better tool; treat the number here as a first-approximation starting point, not an exact prescription.

Safe limits

Two guardrails matter more than hitting an exact figure. The pace should generally stay within about 0.5–1 kg (1–2 lb) per week; faster loss raises the share of muscle lost and the likelihood of regain. And the daily target should not fall below roughly 1,200 kcal for women or 1,500 kcal for men without medical supervision. When a goal and deadline force the target under that floor, the remedy is to lengthen the timeframe or set a more moderate goal rather than to eat dangerously little.

To explore the same numbers from the opposite direction, the Weight Loss Simulator starts from a deficit and projects the time to your goal, while the TDEE Calculator isolates the maintenance figure this calculator builds on.