How do I calculate calories for a lean bulk?

Estimate your maintenance calories (TDEE), then add a surplus. In this tool, lean bulk adds 10%: at 2,500 kcal maintenance, that is 250 extra calories and a 2,750 kcal daily target. Reassess the estimate using your weight trend and training progress.

How much protein does the calculator use?

The tool uses 2.0 g per kg of body weight: 150 g per day for a 75 kg person. This is an assumption for its macro split, not a universal requirement. Age, activity and health can call for individual guidance.

Does a bigger calorie surplus build more muscle?

A larger surplus does not guarantee more muscle. Resistance training and individual response also matter, and additional weight can include fat, water and glycogen. The 12-week split shown here is illustrative, not a validated personal prediction.

What's the difference between BMR and TDEE?

BMR estimates energy expenditure at rest. Maintenance, or TDEE, estimates total daily energy expenditure. This tool adds the surplus to maintenance, not directly to BMR.

How long should a bulk last?

There is no universal duration determined by training experience. Review your goal, trends, training and recovery to decide whether the plan remains appropriate. A calculator cannot automatically decide when to continue or change phases.

Lean bulk vs dirty bulk: which one to choose?

A controlled surplus makes it easier to adjust your intake. Iraki et al. (2019) suggest around 10–20% above maintenance for novice and intermediate bodybuilders, with a more conservative approach for advanced lifters. This tool offers 10%, 15% and 20%; some advanced lifters may need less than its lowest preset.

When should you end a bulk phase?

Review the plan when the trend no longer fits your priorities, training or recovery. A single body-fat percentage does not determine the same decision for everyone. Seek individual advice if symptoms or health concerns arise.

What if I'm not gaining weight despite the surplus?

Estimated maintenance may differ from your actual expenditure, and recorded intake may differ from what you eat. Check the record and the trend over several weeks before adjusting. One weigh-in does not justify a diagnosis or an automatic fixed calorie increase.

Daily calorie target

2,967kcal/d

See details

TrainingSourced · Mifflin-St Jeor formula

Calorie surplus calculator for lean bulking

Estimate your maintenance calories, then compare a 10%, 15% or 20% surplus. Get a daily bulking calorie target and protein, carb and fat targets from your age, height, weight and activity.

By Adrien Grusse

Published April 27, 2026 · Updated October 22, 2026

Sex

Age

yrs

Height

Weight

Activity level

Surplus type

The smallest surplus offered here. Use it as a starting estimate, then adjust to your weight trend and training progress.

Strength training experience

Daily calorie target

2,967kcal/d

Basal metabolic rate

1,740

kcal/d · BMR

Maintenance

2,697

kcal/d · TDEE

Surplus

+270

kcal/d

Estimated macro split

Protein

150 g

20 %

Carbs

385 g

52 %

Fat

92 g

28 %

Protein at 2.0 g/kg · Fat ~28% · Carbs = remainder

Illustrative 12-week projection

Estimated weight gain

+3.1 kg

Of which muscle

+1.4 kg

Of which fat

+1.7 kg

This illustration uses fixed muscle-to-fat assumptions for each training level. It cannot predict your individual body composition or guarantee muscle gain.

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How does the calculation work?

Step 01

Basal Metabolic Rate (BMR)

Mifflin-St Jeor estimates resting calorie needs from sex, age, height and weight. It is a starting estimate, not a measurement of your metabolism.

Step 02

Total Daily Energy Expenditure (TDEE)

An activity multiplier estimates total daily energy expenditure (TDEE). This is your estimated maintenance: the calories used before adding a surplus.

Step 03

Calibrated surplus + macros

Daily calories = estimated maintenance × 1.10, 1.15 or 1.20. For example, 2,500 kcal maintenance gives a 2,750 kcal lean bulk target. The tool sets protein at 2.0 g/kg, fat at 28% of calories and carbs as the remainder.

How many calories should you eat to lean bulk?

A calorie surplus means eating above your maintenance calories. This calculator estimates maintenance first, then adds your selected surplus; the surplus is not your total daily intake.

For example, a 10% surplus on 2,500 kcal maintenance adds 250 kcal, for 2,750 kcal/day. Treat the result as a starting point and adjust using your weight trend, training and recovery.

For a deeper dive — the definition of a calorie surplus, nutrition and training: read the guide to caloric surplus →

Can a calculator predict muscle versus fat gain?

No calculator can reliably predict your personal muscle-to-fat gain ratio. Training experience, your program and the size of the surplus all matter. The projection above illustrates the assumptions of this tool, not a guaranteed outcome.

4 tips to optimize your muscle gain

Understand the protein target

The tool uses 2.0 g/kg as an assumption for its macro split. This does not mean that everyone needs that amount; consider your overall diet and individual circumstances.

Progress in the gym

An appropriate, progressive resistance program provides the training stimulus. Additional calories alone cannot guarantee muscle gain.

Sleep 7–9 hours

Sleep supports recovery. Consider sleep quality and how your training responds; a number of hours cannot predict the amount of muscle you will gain.

Look at your weight trend

Compare measurements under similar conditions and trends over several weeks. Water and digestive contents can affect scale weight; avoid adjusting intake because of one weigh-in.

Frequently asked questions about caloric surplus

Scientific sources

This article draws on 7 peer-reviewed studies and publications, listed below. Every link points to the original source (PubMed, NIH, government agencies, scientific journals).

[1]Helms ER, Aragon AA, Fitschen PJ (2014). Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation. Journal of the International Society of Sports Nutrition. View source ↗PMID : 24864135
[2]Schoenfeld BJ, Aragon AA (2018). How much protein can the body use in a single meal for muscle-building? Implications for daily protein distribution. Journal of the International Society of Sports Nutrition. View source ↗PMID : 29497353
[3]Iraki J, Fitschen P, Espinar S, Helms E (2019). Nutrition recommendations for bodybuilders in the off-season: a narrative review. Sports (Basel). View source ↗PMID : 31247944
[4]Lamon S, Morabito A, Arentson-Lantz E, et al. (2021). The effect of acute sleep deprivation on skeletal muscle protein synthesis and the hormonal environment. Physiological Reports. View source ↗PMID : 33400856
[5]Phillips SM, Van Loon LJ (2011). Dietary protein for athletes: from requirements to optimum adaptation. Journal of Sports Sciences. View source ↗PMID : 22150425
[6]Morton RW, Murphy KT, McKellar SR, et al. (2018). A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. British Journal of Sports Medicine. View source ↗PMID : 28698222
[7]Garthe I, Raastad T, Refsnes PE, et al. (2013). Effect of nutritional intervention on body composition and performance in elite athletes. European Journal of Sport Science. View source ↗PMID : 23574396

About the author

Adrien Grusse

Founder of Micron

Adrien is the founder of Micron, the app that helps more than 150,000 users track their micronutrients daily. Before Micron, he worked on the Growth team at Finary (Y Combinator). Adrien is not a credentialed dietitian — his role here is to translate the scientific literature into accessible content, rigorously. Every article cites peer-reviewed sources (PubMed, Cochrane, recent meta-analyses); no claim is made without a verifiable reference. For individual medical follow-up, consult a healthcare professional.

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