Weight Gain Calculator

For lean muscle gain with minimal fat accumulation, 0.25–0.5% of bodyweight per week is generally recommended by sports nutrition research — for a 70kg person, that's roughly 175–350g per week. Faster gains (0.5–1kg/week or more) are possible but result in a substantially higher proportion of the weight gained being fat rather than muscle, since muscle protein synthesis has a biological ceiling on how quickly it can build new tissue regardless of how large a calorie surplus you provide. This calculator's slower rate options (0.125–0.25kg/week) are aimed at "lean bulking," while faster options suit those less concerned about minimising fat gain.

Your surplus size directly determines the ratio of muscle to fat you'll gain. A modest surplus (200–300 kcal/day above maintenance) provides enough extra energy to support muscle protein synthesis without excessive fat storage, while a larger surplus (500+ kcal/day) does not build muscle proportionally faster — muscle growth is limited by training stimulus and protein synthesis rates, not just calorie availability — so the extra calories beyond what's needed largely convert to fat gain. This is why "dirty bulking" with very large surpluses is now generally discouraged by evidence-based coaches in favour of smaller, more controlled surpluses.

Yes, essentially. Without a resistance training stimulus, your body has no biological signal to prioritise building new muscle tissue with the extra calories from a surplus — the surplus will predominantly be stored as fat regardless of how much protein you eat. Progressive resistance training (gradually increasing weight, reps, or sets over time) is the mechanism that signals your body to direct surplus calories and protein toward muscle repair and growth rather than fat storage. Combining a modest, controlled surplus with a structured, progressive resistance training programme is the combination most strongly associated with favourable muscle-to-fat gain ratios in research.

Research on muscle-building supports 1.6–2.2g of protein per kg of bodyweight per day for individuals in a calorie surplus with a structured resistance training programme — this range consistently shows the strongest muscle protein synthesis response in studies. Eating meaningfully above this range doesn't appear to accelerate muscle growth further; the additional protein calories are simply used for energy or, if part of an overall surplus, contribute to fat storage rather than additional lean tissue. Use our Protein Calculator to set a precise daily gram target based on your bodyweight and goal.

Yes, and this early jump is not primarily fat gain. In the first 1–2 weeks of increasing calorie intake (especially carbohydrate intake), your body typically increases glycogen stores in muscle and liver tissue, and each gram of stored glycogen holds roughly 3 grams of water — this alone can add 1–2kg of "weight" that isn't fat, simply from increased carbohydrate and water storage. Digestive content (more food in the gut at any given time) also adds temporary scale weight. True muscle and fat accumulation happens more gradually over subsequent weeks; don't interpret a fast initial jump as a sign your surplus is too aggressive.

The clearest sign is a gain rate substantially faster than your target (e.g., gaining 1kg+ per week when aiming for lean 0.25–0.5kg/week gains) combined with visibly increasing waist circumference or body fat percentage over several weeks (use our Body Fat Calculator periodically to track this objectively). If you notice this pattern, reduce your daily surplus by 100–200 kcal and reassess after 2–3 weeks. Tracking waist circumference monthly alongside scale weight gives an early, objective warning sign that's more reliable than relying on the mirror or scale weight alone.

Yes, though it often requires a more deliberate approach than for others. So-called "hardgainers" typically have a naturally higher baseline metabolic rate, higher spontaneous daily movement (fidgeting, restlessness — sometimes called NEAT), or simply underestimate how much they're actually eating relative to their true calorie needs. The solution is the same underlying principle — a consistent calorie surplus — but it may require more deliberate meal planning, calorie-dense food choices (nut butters, oils, dried fruit, smoothies), and consistent tracking, since "eating a lot" by feel often falls short of the actual surplus needed for naturally high-metabolism individuals.

Moderate cardio (for cardiovascular health, not excessive volume) is generally fine and doesn't meaningfully interfere with muscle gain for most people, but excessive cardio volume can work against a weight gain goal in two ways: it burns additional calories that effectively shrink your intended surplus (requiring you to eat even more to compensate), and very high training volumes combining heavy cardio with resistance training can create excessive overall fatigue that impairs recovery and strength progression. Most people gaining weight for muscle building keep cardio moderate (2–3 short sessions per week for health) and prioritise their resistance training recovery.

Your recommended calories combine your estimated TDEE (Total Daily Energy Expenditure, based on your BMR and activity level) plus your chosen daily surplus. If your activity level was set higher than your actual movement (or you're naturally quite active), your baseline TDEE will be considerably above the 2,000–2,500 kcal often cited as a rough "average" figure, before any surplus is even added. This is normal and not a sign of an error — larger, more active, or more muscular individuals genuinely require substantially more calories than smaller or less active individuals to gain weight at the same rate.

There's no single universal answer, but many evidence-based approaches suggest bulking phases of roughly 3–6 months for intermediate lifters, followed by a shorter cutting phase (typically 2–4 months) to reduce any excess fat gained, then repeating the cycle. Beginners can often sustain longer bulking phases (6–12 months) since their rate of "newbie gains" muscle growth is faster and more forgiving of a longer surplus period. More experienced lifters approaching their genetic potential often benefit from shorter, more controlled bulk-cut cycles to keep body fat percentage within a reasonable range year-round.

Prioritise nutrient-dense, calorie-dense whole foods: nuts and nut butters, olive oil and avocado, whole grains (rice, oats, quinoa), starchy vegetables (potatoes, sweet potatoes), full-fat dairy, and lean proteins with healthy fats (salmon, eggs). These provide the extra calories needed for a surplus alongside vitamins, minerals, and fibre — supporting overall health during your weight gain phase, unlike a "dirty bulk" approach relying heavily on processed, low-nutrient foods, which can negatively affect blood lipids, energy levels, and digestive health even while technically hitting your calorie target.

Start eating consistently at your recommended calorie target and track your weight weekly (using a rolling average to smooth out normal day-to-day fluctuation from water and food volume). If your average weight gain rate matches your goal, continue as planned; if it's noticeably faster or slower than intended, adjust your daily calories by 100–200 kcal and reassess after 2–3 weeks. Pair this plan with a structured progressive resistance training programme and our Protein Calculator to maximise the proportion of gained weight that becomes lean muscle rather than fat.