Weight Gain Calculator
A 300-calorie daily surplus adds up to 2,100 calories a week, which projects to about 0.6 lb of weight gain per week. This weight gain calculator estimates calorie surplus, projected weekly gain, and a simple time-to-goal from maintenance calories, target intake, and your current and target weight.
Quick answer
Maintenance calories are the baseline for the estimate.
What this tells you
- •Maintenance calories are the baseline for the estimate.
- •The calculator turns your daily surplus into a weekly gain projection.
- •Time to goal is a rough planning estimate, not a promise of scale change.
How to Use
- 1Enter your maintenance calories from recent tracking or a TDEE estimate.
- 2Enter the calorie intake you plan to eat each day.
- 3Enter your current weight and goal weight in pounds or kilograms.
- 4Calculate to see daily surplus, projected weekly gain, and a simple timeline.
- 5Recheck the plan after a few weeks with real weigh-ins and adherence data.
How It Works
Formula
Daily surplus = target calories - maintenance calories
Weekly surplus = daily surplus x 7
Projected weekly gain = weekly surplus / 3,500 kcal per lb or / 7,700 kcal per kg
Weeks to goal = (target weight - current weight) / projected weekly gainThe calculator starts with the gap between your planned intake and estimated maintenance calories. It converts that surplus into a weekly scale-gain estimate by using common planning rules of 3,500 calories per pound and 7,700 calories per kilogram. The goal timeline divides the weight gap by that weekly pace.
Calculation note: values are processed in the order shown above, using the current input units.
Worked Examples
Moderate surplus for a 10 lb goal
A modest surplus stretches the timeline, but it is usually easier to monitor than an aggressive bulk.
Kilogram goal with a smaller pace
This example shows how a small weekly pace can still add up over a few months.
Common mistakes
- Using guessed maintenance calories instead of tracked intake and body-weight trends
- Assuming a larger surplus always means faster lean-mass gain
- Treating the timeline as exact when water, training, and adherence change real outcomes
Limitations
This is a simple planning model. It assumes your maintenance calories stay stable and uses fixed calorie-to-weight conversion rules, which do not capture changes in activity, digestion, water retention, lean-mass partitioning, medications, or clinical needs.