Estimate time to reach a weight gain goal.
The timeline for gaining weight is the gap to your goal divided by the rate you can sustain, and the rate is the decision that matters. A quarter of a kilogram a week needs about a 275 kcal daily surplus and puts roughly sixty percent of the gain into lean mass for someone training properly; pushing to a kilogram a week needs over a thousand extra calories a day and drops the lean share to around thirty percent, because muscle protein synthesis has a ceiling that eating cannot raise. Gaining ten kilograms therefore takes about eight months at the slow rate and ten weeks at the fast one — but the fast route arrives with several kilograms more fat, which then has to be dieted off at a cost in muscle. Slow is usually the shorter route to the physique people actually want.
Time to a weight-gain goal
Weight to gain = goal - current; weeks = weight to gain / weekly gain; months = weeks / 4.345; daily surplus = weekly gain x 7700 / 7; daily intake = maintenance + daily surplus
Educational estimates only, not medical or dietetic advice. Unexplained difficulty gaining weight can indicate an underlying medical condition, and deliberate weight gain is not appropriate for everyone. Speak to a doctor or registered dietitian before making substantial dietary changes.
Because the rate at which muscle can be built is capped by training and protein synthesis, not by calories. Beyond about half a kilogram a week the extra weight is mostly fat, which you then have to lose — usually at a cost in the muscle you just built.
Roughly 1-1.5% of body weight per month in the first year of serious training, halving in the second and slowing further after that. Anyone past their first couple of years should plan on the slower end of these rates.
Add 150-200 kcal a day and reassess after two weeks. Maintenance estimates are approximate and appetite adapts upward, so an intake that produced a surplus a month ago may now be maintenance.