How big should my surplus be?

Most lifters do best on +200 to +400 kcal/day. Larger surpluses just add fat once you are past the beginner phase. Beginners can sometimes tolerate +500–600 because their growth rate is higher.

Why does experience level slow my gains so much?

Muscle protein synthesis becomes harder to drive as you approach your genetic ceiling. Beginners gain quickly because they are starting far below it. Intermediates and advanced lifters gain roughly half and a quarter of beginner rates respectively.

Why 2.0 g/kg protein?

It sits in the middle of the ISSN-recommended 1.6–2.2 g/kg range for active lifters and is a safe default during a surplus where protein is plentiful anyway.

What if I gain more than the projected weekly amount?

You're likely adding fat as well as muscle. Drop the surplus by 100–200 kcal/day and re-check after 2–3 weeks.

Does this tool save my data?

No. TDEE, weight, and selections stay in your browser and are cleared when you close the tab.

Is the muscle gain calculator free?

Yes — completely free, no signup or limits.

Muscle Gain Calculator

Plan a bulk: calorie target, protein, and weekly weight-gain projection by training age.

Written by Golam Rabbani, Founder & Lead Engineer — Last updated 2026-05-01

This interactive tool requires JavaScript. Read the formula and worked example below; you can compute the result by hand.

How to use this muscle gain calculator

Enter your TDEE — use the TDEE calculator first if you don't know it.
Toggle kg or lbs and enter your current bodyweight.
Pick a surplus size: Lean (+200), Standard (+400), or Aggressive (+600) kcal/day.
Choose your training experience: Beginner, Intermediate, or Advanced.
Press Calculate to see your daily calorie target, protein target, and weekly and monthly weight-gain projections.

About this muscle gain calculator

The muscle gain calculator sets a daily calorie target by adding a chosen surplus to your TDEE, sets protein at 2.0 g/kg of bodyweight, and projects weekly and monthly weight gain based on experience-level multipliers — 0.5%/week of bodyweight for beginners, 0.25%/week for intermediates, and 0.125%/week for advanced trainees. Monthly gain is the weekly figure × 4.345 (the average number of weeks in a month).

Surplus ranges are informed by Helms ER, Aragon AA, Fitschen PJ. "Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation" (J Int Soc Sports Nutr 2014;11:20) and the broader "Pyramid of Muscle Growth" framework, which advise a small to moderate surplus to favour lean over fat gain. The training-experience rates draw on Lyle McDonald's widely cited "Generic Bulking Routine" novice/intermediate/advanced gain table. This is an estimate for informational purposes and is not a substitute for advice from a registered dietitian or qualified clinician.

For example, a 75 kg intermediate trainee with a TDEE of 2,600 kcal/day on a Standard (+400) surplus: target intake = 3,000 kcal/day; protein = 75 × 2.0 = 150 g/day; weekly gain = 75 × 0.0025 = 0.19 kg; monthly gain ≈ 0.19 × 4.345 ≈ 0.81 kg. The tool is useful for matching surplus size to training age so a beginner doesn't under-eat and an advanced lifter doesn't over-eat into unwanted fat gain.

FAQ

How big should my surplus be?: Most lifters do best on +200 to +400 kcal/day. Larger surpluses just add fat once you are past the beginner phase. Beginners can sometimes tolerate +500–600 because their growth rate is higher.
Why does experience level slow my gains so much?: Muscle protein synthesis becomes harder to drive as you approach your genetic ceiling. Beginners gain quickly because they are starting far below it. Intermediates and advanced lifters gain roughly half and a quarter of beginner rates respectively.
Why 2.0 g/kg protein?: It sits in the middle of the ISSN-recommended 1.6–2.2 g/kg range for active lifters and is a safe default during a surplus where protein is plentiful anyway.
What if I gain more than the projected weekly amount?: You're likely adding fat as well as muscle. Drop the surplus by 100–200 kcal/day and re-check after 2–3 weeks.
Does this tool save my data?: No. TDEE, weight, and selections stay in your browser and are cleared when you close the tab.
Is the muscle gain calculator free?: Yes — completely free, no signup or limits.