General information, not medical advice. Check with a doctor or registered dietitian before a big diet change, especially if you have a medical condition, are pregnant, or have a history of disordered eating.
Muscle gain calculators turn one number, the calories that hold your weight steady, into a small daily surplus, a protein target and a weekly rate of gain you can check against the scale. The seven tools in this category cover the same ground from different angles: lean bulking, larger bulks, healthy weight gain, bodybuilding phases and the maintenance figure underneath all of them. This page gives you the published numbers in one place, explains which tool to open for your situation, and works through a complete hypothetical example so you can see how the pieces add up.
The numbers at a glance
Off-season figures from Iraki et al. (2019), a narrative review of nutrition for bodybuilders, plus the protein plateau from Morton et al. (2018), a meta-analysis of protein supplementation with resistance training.
Target
Published figure
Source
Calorie surplus
About 10–20% above maintenance
Iraki 2019
Rate of gain
About 0.25–0.5% of body weight per week (novice and intermediate lifters)
Iraki 2019
Protein
1.6–2.2 g per kg per day
Iraki 2019
Protein plateau
Added gains levelled off beyond about 1.62 g per kg per day
Morton 2018
Protein per meal
0.40–0.55 g per kg
Iraki 2019
Fat
0.5–1.5 g per kg per day
Iraki 2019
Carbohydrate
At least 3–5 g per kg per day
Iraki 2019
Scope
Everything in this category is about one phase: eating above maintenance on purpose, to support muscle growth from resistance training. The tools are the TDEE Bulking Calculator, the Lean Bulk Calorie Calculator, TDEE for Muscle Gain, Muscle Gain Calorie Surplus, the Maintenance Calories Calculator, the TDEE Calculator for Weight Gain and the TDEE Calculator Bodybuilding guide. They overlap deliberately, because people search for the same problem in different words, but each one leans toward a particular reader.
What these tools do not do is build muscle. Training does that. Calories and protein make growth possible, and the surplus only pays off when it is paired with progressive resistance training and enough recovery. A calculator can stop you eating too little to grow or so much that most of the gain is fat; it cannot replace the work in the gym.
Maintenance first
Every number in a gaining phase is a percentage of maintenance, so an error there carries straight through. If your maintenance estimate is 200 kcal too high, a planned 10% surplus may be closer to 3%, and you will wonder why nothing is happening. If it is 200 kcal too low, the surplus is larger than you meant and fat gain speeds up.
That is why the Maintenance Calories Calculator sits in this group even though it does not mention bulking in its name. It explains three ways to find the number, from formula estimates to a few weeks of steady eating and weighing, and how to tell genuine maintenance from slow drift. If you have been tracking your intake and weight for a while, your observed maintenance is a better base than any equation.
For lifters, the activity multiplier is the usual weak point. Hard training several days a week tempts people to choose the site's very active (1.725) or extra active (1.9) settings, but the hours outside the gym often say otherwise. A desk job plus regular lifting is frequently closer to moderately active (1.55). Choosing the lower setting and letting the scale correct you is safer than starting high.
Picking a tool
Start with the one that matches who you are right now.
New to lifting, or wanting to stay lean while gaining: the Lean Bulk Calorie Calculator keeps the surplus small and explains how to tell a lean bulk from a stalled one.
Choosing between a smaller and a larger bulk: the TDEE Bulking Calculator compares surplus sizes side by side and covers when to end a bulk.
Stuck on the 250 versus 500 kcal question: Muscle Gain Calorie Surplus argues that surplus size should follow your gain rate, and works the numbers for three example TDEEs.
Wanting the overall picture of how surplus, protein, training and sleep interact: TDEE for Muscle Gain is the broadest of the group.
Underweight, or struggling to gain anything at all: the TDEE Calculator for Weight Gain covers healthy gain, appetite problems and tracking errors that hide a real surplus.
Training for a physique contest, or running separate prep and off-season phases: the TDEE Calculator Bodybuilding guide sets both phases from one maintenance figure.
Unsure of your starting point: the Maintenance Calories Calculator, before any of the above.
Sizing the surplus
Iraki and colleagues' review puts the off-season surplus at roughly 10 to 20% above maintenance, paired with a target gain of about 0.25 to 0.5% of body weight per week for novice and intermediate lifters. The site's calculator offers two gaining settings that line up with that range, a lean bulk at +10% and a moderate bulk at +20%. These settings are site defaults, not study findings, but they sit at the two ends of the published range.
The more useful way to think about it is that the weekly rate is the target and the surplus is the tool you adjust to reach it. Start at the lower end if you are relatively lean, have a few years of training behind you, or dislike gaining fat. Start nearer the upper end if you are new to lifting, are underweight, or find it hard to eat enough. Then check the trend after three or four weeks. If you are gaining faster than about 0.5% of body weight a week, trim the surplus; if the scale has not moved at all, add to it.
This is the core argument of Muscle Gain Calorie Surplus and the Lean Bulk Calorie Calculator, and the reason the two pages mostly discourage large bulks. A surplus bigger than your rate of muscle growth can use ends up stored as fat, which later needs a longer cut to remove.
Worked example
An explicitly hypothetical lifter: a 24-year-old man, 180 cm, 73 kg, moderately active (the site's 1.55 multiplier). Maintenance uses Mifflin-St Jeor (10 × weight + 6.25 × height − 5 × age + 5). Ranges apply the Iraki 2019 and Morton 2018 figures above. Computed exactly, rounded to whole kcal or grams at the end.
Item
Calculation
Result
Resting burn (BMR)
10×73 + 6.25×180 − 5×24 + 5
1,740 kcal
Maintenance (TDEE)
1,740 × 1.55
2,697 kcal
Lean bulk, +10%
2,697 × 1.10
2,967 kcal (surplus 270 kcal)
Moderate bulk, +20%
2,697 × 1.20
3,236 kcal (surplus 539 kcal)
Weekly gain target
73 kg × 0.25% to 73 kg × 0.5%
About 183–365 g per week
Protein, published range
73 × 1.6 to 73 × 2.2
117–161 g per day
Protein, plateau point
73 × 1.62
118 g per day
Protein per meal
73 × 0.40 to 73 × 0.55
29–40 g
Fat
73 × 0.5 to 73 × 1.5
37–110 g per day
Carbohydrate floor
73 × 3 to 73 × 5
At least 219–365 g per day
Hypothetical inputs, not advice for a real person. At the lean-bulk target, 118 g protein (472 kcal) and 80 g fat (720 kcal) leave 1,775 kcal, or about 444 g of carbohydrate, comfortably above the carbohydrate floor.
Protein
Protein is the macro people most often overshoot during a bulk, usually because more feels safer. The published figures suggest a ceiling on the benefit. Iraki's review recommends 1.6 to 2.2 g per kg of body weight per day in the off-season. Morton and colleagues' 2018 meta-analysis, which pooled resistance-training studies with and without protein supplementation, found that added gains in fat-free mass levelled off beyond about 1.62 g per kg per day. The 2017 International Society of Sports Nutrition position stand gives 1.4 to 2.0 g per kg per day for most exercisers.
Read together, these put a sensible daily target somewhere from the mid-1s to around 2 g per kg, with no strong reason to go far above it during a surplus, when energy is plentiful. Every extra gram of protein in a fixed calorie budget also takes the place of carbohydrate, the macro the review sets a training floor for.
Spread matters too. Iraki's figure of 0.40 to 0.55 g per kg per meal works out at 29 to 40 g for the hypothetical lifter above, which is easier to reach across three to six meals than in one or two large ones.
Bodybuilding phases
Physique athletes alternate between two phases, and the TDEE Calculator Bodybuilding guide covers both. The off-season uses the Iraki figures in the table at the top. Contest preparation uses a separate set from Helms and colleagues' 2014 review: lose about 0.5 to 1% of body weight per week, eat 2.3 to 3.1 g of protein per kg of lean body mass, and take 15 to 30% of calories from fat. The same review flags the risks of extreme prep practices, including disordered eating and dehydration, which is why the guide treats coaching and medical oversight as part of the process.
The practical link between the phases is the maintenance number. Both are set as departures from it, and a lifter who has tracked maintenance carefully through an off-season starts prep with a much better estimate than one who has only ever used a formula. Entering body fat in the calculator, so it switches to the lean-mass formula it uses (370 + 21.6 × lean body mass in kg), also helps heavily muscled lifters, whose weight-only estimate tends to read low.
Common errors
Starting from an inflated maintenance number, usually by choosing a high activity setting because training feels hard.
Picking a surplus by habit (250 or 500 kcal) instead of by the weekly rate it produces.
Judging progress from single weigh-ins. A week of muscle gain is small enough to disappear inside ordinary day-to-day fluctuations, so use weekly averages.
Raising protein far above the plateau while letting carbohydrate fall below the 3–5 g per kg floor that supports training.
Never ending the bulk. Without a planned end point or a body-fat limit, a gaining phase drifts into steady fat gain.
Recalculating too rarely. As body weight rises, maintenance rises with it, and an unchanged intake slowly turns a surplus back into maintenance.
Reading the scale
The weekly gain target is small enough that daily noise can hide it completely. For the hypothetical 73 kg lifter, 183 to 365 g a week is a fraction of a kilogram, easily masked by changes in water and food in the gut. Weigh at the same time each day, average each week, and compare averages three to four weeks apart before changing the surplus.
Gains also slow as training age increases. In a 1995 study of 157 male athletes, Kouri and colleagues found that men who had not used anabolic steroids topped out at a fat-free mass index of about 25. The closer you get to that kind of ceiling, the less muscle a surplus can build, which is why the Iraki rate range is stated for novice and intermediate lifters and why experienced lifters usually do better at the lower end of the surplus range.
When the trend has been on target for a few months, or body fat has crept up more than you are comfortable with, it is time to move to maintenance or a cut. The weight loss calculators hub covers that next phase, and the body recomposition hub covers the alternative of losing fat and building muscle at maintenance.