Calorie deficit and goal date calculator

The pace is a percentage of your current weight each week, so each week’s step is worked out from the weight the week before. The projection steps one week at a time and counts the last part-week as a fraction. This is how Pendum Macros projects its goal date. Imperial inputs are converted exactly (1 lb = 0.45359237 kg) first.

step       = weight × pace / 100
next week  = weight − step   (lose)
           = weight + step   (gain)
last week  = left / step
             (once left ≤ step)
days       = ceil(weeks × 7)
goal date  = today + days

first week = min(distance, step)
kcal a day = first week × 7,700 / 7
maintenance ≥ 1,500 + kcal a day  (lose)

For 80 kg to 75 kg at 0.5% a week, the first step is 0.4 kg. After 12 weeks the weight is 75.33 kg, the 13th step is 0.38 kg and 0.33 kg is left, so the goal comes at 12.9 weeks, 91 days from today. The daily change at the start is 0.4 × 7,700 / 7 = 440 kcal below maintenance.

Paces. A loss of 0.25%, 0.5%, 0.75% or 1% a week, or a gain of 0.1%, 0.25% or 0.5% a week. Pendum Macros marks 0.5–1% as the band that suits most people losing weight and 0.1–0.25% for gaining; a higher gain adds more fat alongside the muscle. Because the step is a share of weight, it shrinks as you lose and grows as you gain, and the calorie change follows it.

7,700 kcal per kilogram. This is the familiar 3,500 kcal per pound, about 32.2 MJ/kg, and it is a short-term approximation. As weight falls, the energy the body uses falls with it, so a fixed deficit brings less loss over time than this model shows (Hall and colleagues 2011). The energy in a kilogram lost also depends on body fat: it is lower for leaner people, who lose more lean tissue (Hall 2008). The NIDDK Body Weight Planner models both for a longer plan.

Limits. Pendum Macros does not set a daily target under 1,500 kcal, and it does not plan a cut when the current or goal weight is a BMI under 18.5. This page asks for neither your maintenance nor your height, so it applies neither. For a cut it states the maintenance the pace needs to keep intake at 1,500 kcal or more: for the example, 1,500 + 440 = 1,940 kcal a day.

At 520 weeks or more, no date is shown, as in the app. Under a week, the time is given in days. A change that rounds to 0.00 kg or lb counts as no change.