What this tool does
TDEE is estimated, then increased by your surplus percent. You also see the daily extra calories and a rough weekly gain using the same 7,700 kcal/kg sketch. This is for people who are actually lifting, not for eating in a surplus on the couch and calling it hypertrophy.
How it works
Target = TDEE × (1 + surplus%/100). New lifters can gain a bit faster; trained lifters usually want the small end so fat gain stays boring. Protein should sit in the muscle range (about 1.6–2.2 g/kg) so the surplus has amino acids to work with.
Formula and methodology
TDEE = Mifflin-St Jeor BMR × activity. Target = TDEE × (1 + surplus%/100). Rough kg/week ≈ (target − TDEE) / (7,700/7). Same honest limit as deficit math: the weekly line is a sketch. Tissue gained is mixed.
How to interpret the result
5–8% is a lean-bulk nudge. 15–20% is easier to see on the scale and easier to regret in a shirt. If waist jumps weekly while lifts stall, the surplus is outrunning the training. Rest days still get the surplus; you do not “earn” food only in the gym.
Example
TDEE 2,760 kcal + 10% ≈ 3,040 kcal, about 280 kcal extra, paper gain near 0.25 kg/week. Pair with ~150 g protein for an 80 kg lifter. That extra is a yogurt and a banana, not a second dinner as a personality.
Common mistakes
- A 20% surplus with two easy gym sessions and calling it a bulk.
- Skipping protein because “calories are anabolic.”
- Changing the surplus every time morning weight ticks up from glycogen.
- Cutting all carbs “to stay lean” while in a surplus — you just made training worse.
When this estimate may be off
- You are not training with progressive overload.
- TDEE was already a surplus and you stacked another 10%.
- Appetite drugs, illness, or a growth period this adult equation ignores.
- Weight gain is mostly edema or a new creatine loading week.