Bulking calorie calculator
Enter your stats, activity level and training age, then pick a lean, standard or aggressive surplus. You get your maintenance calories, a daily target to eat and how much of the expected monthly gain is likely to be muscle rather than fat.
Standard surplus. At your training age, about 0.6 kg of the expected 1.0 kg monthly gain should be muscle, the rest mostly fat with some water.
How the bulking calorie calculator works
A calorie surplus means eating more than your body burns in a day, so it has spare energy to build new tissue, mostly muscle if you are training hard, some fat regardless. The calculator gets there in three steps.
Step 1: resting energy (BMR)
Your basal metabolic rate is what you burn lying still for 24 hours: breathing, circulation, keeping organs running. We estimate it with the Mifflin St Jeor equation, which uses weight, height, age and sex and is the most accurate of the common formulas for most adults.
Step 2: maintenance calories (TDEE)
BMR is multiplied by an activity factor to give total daily energy expenditure, your maintenance calories. Eat that amount and your weight holds steady. The factor runs from 1.2 for a desk job with no training up to 1.9 for athletes or physical work.
Step 3: the surplus
The calculator adds a percentage on top of maintenance: 10 percent for a lean bulk, 15 to 20 percent for a standard bulk, 25 percent for an aggressive bulk. For someone maintaining on 2,600 kcal that is roughly 260, 455 and 650 kcal a day. What comes out is your daily target.
Why Mifflin St Jeor, and when another equation fits better
Several equations estimate resting energy and they all use the same inputs but drift apart at the edges, because they were built on different populations.
Mifflin St Jeor (used here)
Published in 1990 from 498 adults across a wide range of weights. A 2005 systematic review found it predicted measured metabolic rate within about 10 percent for the largest share of people, lean and obese alike, which is why it is the default in clinical settings and in this calculator.
Katch McArdle and Cunningham
Both use lean body mass instead of total weight, so they need a reliable body fat percentage from a DEXA scan or consistent calipers. For a lean, experienced lifter that can edge out Mifflin St Jeor. For everyone else a guessed body fat number introduces more error than it removes. Get a number from the body fat calculator before switching.
Harris Benedict
The 1919 original, revised in 1984. It tends to overestimate by around 5 percent, more so in heavier people, because the sample was small and lean. There is no reason to prefer it over Mifflin St Jeor now.
Whichever equation you use, treat the maintenance figure as an estimate to be tested, not a fact. The TDEE calculator covers the maintenance side of this in more detail if you want the full comparison before you add a surplus on top.
Choosing your surplus: lean, standard or aggressive
How big a surplus should be depends on how fast you want the scale to move and how much fat gain you are willing to accept alongside the muscle. None of the three presets is wrong, they trade speed for body composition.
Lean bulk (about +10%, 200 to 300 kcal)
The smallest surplus that reliably supports muscle growth without much fat gain. Progress is slow to see week to week, which is the point: nearly everything you gain is either muscle or the extra water and glycogen that comes with training harder. Best choice if you are already lean or would rather stay close to your current waistline.
Standard bulk (+15 to 20%)
The middle ground and the one most people should start with. Enough energy to notice steady gains in the mirror and on the bar within a month, without the surplus outrunning what your body can actually turn into muscle.
Aggressive bulk (+25%)
Only makes sense for a genuine beginner in their first year of training, when the body can build muscle fast enough to use the extra energy, or for someone very lean with room to add fat. Past that window an aggressive surplus mostly adds fat, because muscle can only be built so fast regardless of how much you eat. This preset sits above the 10 to 20 percent range the cited research covers, and is offered deliberately, for beginners and very lean lifters only.
Where you are starting from matters as much as the preset
The three presets assume you are a reasonable candidate for a bulk in the first place. Carrying more body fat than you are comfortable with before you start is a common reason a bulk gets abandoned partway through, once the extra weight reads as more of what was already there rather than new muscle. If that describes you, a deficit first puts the surplus that follows onto a leaner base, so what you build actually looks like progress in the mirror. Check where you stand with the body fat calculator before you commit to a preset. Sitting close to your own comfort line either way, the body recomposition calculator covers gaining muscle and losing fat at maintenance, without picking a surplus at all.
Expected gain by training age
How much of your weight gain ends up as muscle depends more on training age than on diet. A newly trained lifter can build muscle quickly even in a small surplus; someone who has trained hard for years is working with a much narrower window, and extra calories beyond it become fat. The weekly rate of gain below follows the range Iraki et al. describe for natural lifters, narrowed as training age rises. Figures assume a 75 kg (165 lb) lifter; the calculator uses your own weight.
The muscle share column is an editorial convention, not a figure measured by any single study: no source we cite reports a novice, intermediate and advanced breakdown of how much of a surplus becomes muscle. It is consistent with Garthe et al., who found a faster, larger surplus added more fat with no extra lean mass gained compared with a slower one in elite athletes, but Garthe reports only whole-group averages over 8 to 12 weeks, not a partition by training age. Treat the percentages as illustrative of the general pattern, not a measured ratio for your own training age.
The advanced row's weekly rate also extrapolates below the published range: Iraki et al. give advanced lifters 0.25 to 0.5% body weight a week and simply advise going more conservative within that range, not below it. The 0.2 to 0.25% here narrows the bottom end further for lifters several years in, the same way the aggressive surplus preset extends above the surplus range the cited research covers.
| Training age | Weekly rate | Monthly gain (75 kg lifter) | Muscle share | Best surplus |
|---|---|---|---|---|
| Novice, under 1 year | 0.4 to 0.5% body weight | 1.3 to 1.6 kg (2.9 to 3.5 lb) | 70 to 80% | Lean to standard |
| Intermediate, 1 to 3 years | 0.3 to 0.4% body weight | 1.0 to 1.3 kg (2.2 to 2.9 lb) | 50 to 60% | Standard |
| Advanced, 3+ years | 0.2 to 0.25% body weight | 0.65 to 0.8 kg (1.4 to 1.8 lb) | 30 to 40% | Lean, aggressive rarely justified |
How to use the number
Treat the target as a starting point. Weigh yourself daily and average each week; if the weekly average is climbing at roughly the rate for your training age, keep going. If it is flat after two weeks, add 100 to 150 kcal. If it is climbing faster than the table suggests, most of the extra is going to fat, so pull back.
Train to earn the surplus
A calorie surplus builds muscle only alongside progressive resistance training. Without a training stimulus that gets harder over time, the extra energy has nowhere useful to go and becomes fat gain on its own. Track your lifts, not just your food.
Watch the waist, not just the scale
Body weight cannot tell muscle from fat. A tape measure around the waist, taken weekly under the same conditions, is the simplest check. A waist that holds steady while the scale climbs is a good sign; a waist growing as fast as the scale means the surplus is too big.
Get protein right
Protein needs do not fall during a bulk. Aim for 1.6 to 2.2 g per kg of body weight and let carbohydrate cover the rest of the surplus, since it fuels the training that earns the muscle. The macro calculator splits the target for you.
When to end the phase
Most bulks run three to six months before the trade off between muscle and fat gain stops being worth it. A sensible endpoint is either a set amount of time agreed in advance, or a waist measurement or body fat percentage you are not willing to pass. Reaching either is the signal to move to a shorter maintenance phase or a lean phase, not a reason to push the surplus further.
A worked example: a 75 kg intermediate over 12 weeks
Take a 75 kg (165 lb) man, two years of consistent training behind him, moderately active, with the calculator putting maintenance at 2,700 kcal. He picks a standard bulk at 17.5 percent, landing on a target of roughly 3,170 kcal a day, with protein set at 1.8 g per kg (about 135 g) and carbohydrate and fat splitting the rest.
Weeks 1 to 2, his weekly average barely moves. That is normal: the body needs a stretch of consistently higher intake before the trend on the scale separates from day to day noise, and it is not a sign the surplus is failing.
Weeks 3 to 6, the average starts climbing at close to 0.35 percent of body weight a week, in the middle of the intermediate range in the table above. His waist measurement, taken every Monday morning before food, holds close to steady.
Week 7, the average has been flat for two straight weeks. He adds 150 kcal, taking the target to about 3,320 kcal, and the average resumes climbing at roughly the same rate as before.
Week 12, the block ends with a gain in the region of 2.5 to 3 kg, a small increase in waist measurement, and every main lift up 5 to 8 percent. That is close to what the training age table predicts for an intermediate over 12 weeks (roughly 2.8 to 3.6 kg at this bodyweight, three times the monthly figure), the flat weeks at the start and the week 7 plateau accounting for the difference. Most of the gain reads as muscle and training related water, with a smaller amount of fat that is expected at this stage.
From here he has two honest options: keep going at the new, heavier maintenance, recalculating rather than assuming the number from week one still applies, or bank the gains and spend four to six weeks at maintenance before deciding whether to run another bulk or start a lean phase. Neither is a mistake. What matters is choosing on purpose rather than drifting past the point the surplus was doing its job.
When the plateau is not really a plateau
A flat weekly average for a few days is usually noise, not a stalled surplus. Sodium intake, the carbohydrate you ate the day before you weighed in, hydration and where you are in a training cycle can each move the scale in either direction, and the water stored alongside glycogen means a heavier training week alone can nudge the number up before any tissue has actually changed. Only react to a trend that holds across a full two week average, not a single reading.
Before you touch the calorie target, rule out the boring causes first. Are you actually eating the amount the calculator gave you, weighed and logged rather than estimated by eye, and is sleep and stress roughly normal for you. A genuine plateau, once those are ruled out, is the point to add 100 to 150 kcal, not before.
Signs the surplus is too big
A surplus is a starting estimate, not a fixed prescription, so check it against what actually happens over a few weeks.
Weekly weight gain well above the table. If you are intermediate and gaining 1 percent of body weight a week, the extra is fat, not a faster route to muscle.
Waist growing as fast as the scale. A stable or slowly climbing waist alongside steady scale weight means the surplus is doing its job. A waist tracking the scale closely means too much of the gain is fat.
Strength stalling despite the extra food. If your lifts are not moving up over four to six weeks in a surplus, the extra calories are not being used for muscle, whatever your training age.
Common mistakes
Starting with an aggressive surplus by default. Most people are not beginners and are not lean enough to justify 25 percent over maintenance. Start standard and adjust from there.
Treating "bulk" as permission to eat anything. The surplus is a calorie target, not a free pass. Ultra processed food still needs to fit the number, and protein and training still decide how much of the gain is muscle.
Skipping progressive overload. Extra food without extra training stimulus over time builds fat, not muscle.
Never recalculating. A surplus set at 70 kg is a bigger surplus at 78 kg. Rerun the numbers every 4 to 5 kg gained.
Bulking indefinitely. Most lifters do better cycling a bulk of several months with a shorter maintenance or slight deficit phase, rather than surplus eating year round.
Judging by the scale alone. Two people can gain the same weight in a month and come away with very different results. Photos, a waist measurement and how the bar feels tell you more than the number on the scale ever will.
How coaches use a bulking calorie calculator
For a coach the number is the opening move of a mass gain phase, not the whole plan. It sets a starting target; the work is in watching the trend and adjusting before a client overshoots into an unplanned amount of fat gain.
A workable routine: calculate the target at the start of the phase, set protein first, then review the weekly weight average and waist measurement every week. Move the surplus in steps of 100 to 150 kcal and never more than once every two weeks, so you can tell what caused a change.
Scraler runs that loop without spreadsheets. Set a calorie and macro target per client, build the training programme that earns the surplus, and see weekly weight and check-in photos in one view instead of chasing messages. See nutrition coaching and workout programming, or read how hybrid personal training packages a bulking phase with in person and remote coaching.
Frequently asked questions
- How many calories should I eat to bulk?
- Add 10 to 25 percent to your maintenance calories, depending on how fast you want to gain. For someone maintaining on 2,600 kcal that is roughly 2,860 to 3,250 kcal a day. Most people should start with a standard surplus of 15 to 20 percent.
- What is a good calorie surplus for muscle gain?
- A surplus of 10 to 20 percent above maintenance covers most people. Beginners and very lean lifters can lean toward the higher end; anyone with a few years of training history or a higher body fat percentage should stay closer to 10 percent.
- How much weight should I gain per week when bulking?
- Roughly 0.25 to 0.5 percent of body weight a week, the range Iraki et al. describe for novice and intermediate lifters, with advanced lifters advised to go slower. At 80 kg that is 0.2 to 0.4 kg a week, or about 0.9 to 1.7 kg a month.
- How much of my weight gain will be muscle?
- It depends on training age. As a rough guide, beginners can turn 70 to 80 percent of the gain into muscle; intermediates land closer to 50 to 60 percent; advanced lifters, 30 to 40 percent, with the rest mostly fat and water. These are an editorial convention illustrating the general pattern, not percentages measured by a specific study. Progressive training and enough protein push the ratio toward muscle at every level.
- Lean bulk vs dirty bulk, which is better?
- A lean bulk, around a 10 percent surplus, builds nearly as much muscle as a larger surplus while adding much less fat, so it leaves less to clean up later. A dirty bulk, eating well above maintenance without much control, adds weight faster but most of it beyond your training age ceiling is fat.
- How long should a bulking phase last?
- Most lifters do well with three to six months of a surplus, then a few weeks at maintenance or a slight deficit before the next phase. Advanced lifters, whose fat gain climbs faster relative to muscle, benefit from shorter bulking blocks than beginners.
- Do I need a calorie surplus to build muscle?
- Not always. Complete beginners and people returning after a long break can build muscle at maintenance or even in a small deficit, a state sometimes called body recomposition. Once that window closes, a surplus becomes the more reliable way to keep gaining size.
- How much protein do I need while bulking?
- Around 1.6 to 2.2 g per kg of body weight a day. A surplus does not reduce protein needs, and adequate protein is one of the main things that determines how much of your weight gain is muscle rather than fat.
- Should beginners bulk or cut first?
- If you are new to training and not carrying much excess body fat, bulk first. Beginners build muscle fastest of anyone, so it is the point in training where a surplus pays off the most. Leave cutting for once that early progress has slowed.
- How do I know if I am gaining fat too fast?
- Compare your weekly weight gain with the rate for your training age and check your waist measurement alongside the scale. If the waist is climbing as fast as body weight, or the gain is well above the table, cut the surplus by 100 to 150 kcal.
- Should I recalculate my calories as I gain weight?
- Yes. Maintenance rises as you get heavier, so a target set at your starting weight understates the surplus once you have gained a few kilograms. Rerun the calculator every 4 to 5 kg gained.
- Should I bulk if I am already carrying a lot of body fat?
- Not straight away. Carrying more fat than you are comfortable with is a common reason a bulk gets abandoned partway through, once the extra weight reads as more fat rather than new muscle. A deficit first, checked with the body fat calculator, puts the surplus that follows onto a leaner base. Sitting close to your own comfort line either way, the body recomposition calculator covers gaining muscle and losing fat at maintenance instead.
Sources
- Mifflin MD et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr, 1990The BMR equation used here.
- Frankenfield D et al. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults. J Am Diet Assoc, 2005Systematic review that found Mifflin St Jeor the most accurate of the common equations.
- FAO/WHO/UNU. Human energy requirements. Report of a Joint Expert Consultation, 2004The physical activity level (PAL) concept behind the activity factors. The 1.2 to 1.9 ladder itself is the conventional chart most calculators use, not an FAO table.
- Iraki J, Fitschen P, Espinar S, Helms E. Nutrition recommendations for bodybuilders in the off-season: a narrative review. Sports, 2019Surplus of 10 to 20%, rate of weight gain of 0.25 to 0.5% body weight per week narrowed as training age rises, and the 1.6 to 2.2 g/kg protein range.
- Slater GJ et al. Is an energy surplus required to maximize skeletal muscle hypertrophy associated with resistance training? Front Nutr, 2019Why a large surplus is not required for hypertrophy, and the unfavourable composition of weight gained without a training stimulus.
- Garthe I, Raastad T, Refsnes PE, Sundgot-Borgen J. Effect of nutritional intervention on body composition and performance in elite athletes. Eur J Sport Sci, 2013Elite athletes gaining weight faster on a larger surplus added more fat, with no difference in lean mass gained, versus a slower ad libitum gain.
- Helms ER et al. Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation. J Int Soc Sports Nutr, 2014Contest prep nutrition for natural bodybuilders in an energy deficit; supports higher relative protein and more conservative rates of change for lean, experienced lifters.
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