Macro Calculator for Muscle Gain
Dial in the calorie surplus and macro split that builds lean muscle without piling on excess fat.
Building muscle requires three things: a progressive training stimulus, enough protein to repair and grow tissue, and a modest calorie surplus to fuel it. Eat too little and you spin your wheels; eat too much and a "bulk" just becomes fat gain.
This calculator is pre-set to a muscle-gain goal. It estimates your maintenance calories, adds a lean-bulk surplus, and splits the total into a carb-forward ratio (25% protein / 50% carbs / 25% fat) that powers hard training and recovery. Enter your details below for your daily targets.
Lean bulk vs dirty bulk
A lean bulk uses a modest surplus (this calculator applies ~20% above maintenance) so most of the weight you gain is muscle, not fat. "Dirty bulking" — eating everything in sight — adds fat you will only have to diet off later. Aim for roughly 0.25–0.5 kg of gain per month if you are past the beginner stage; faster gains usually mean more fat.
Protein and carbs for growth
Protein stays high (around 1.6–2.2g per kg) to maximise muscle protein synthesis, while carbs do the heavy lifting for energy — fuelling your sessions, replenishing glycogen, and supporting recovery. That is why the muscle-gain split leans carb-heavy at 50%. Prioritise nutrient-dense carbs like oats, rice, potatoes and fruit over empty sugars.
Hitting a surplus as a Kiwi
Eating enough can be the hard part when bulking. Calorie-dense, affordable options in NZ include oats, peanut butter, full-fat milk, rice, mince and eggs. A homemade shake (milk, oats, peanut butter, banana, whey) is an easy way to add a few hundred calories. Remember NZ food labels list kilojoules — divide kJ by 4.184 to convert to calories.
Frequently Asked Questions
What are the best macros for building muscle?
A carb-forward split works well for muscle gain: roughly 25% protein, 50% carbs and 25% fat, eaten in a modest calorie surplus. High carbs fuel training and recovery while protein drives growth. This calculator applies that ratio automatically.
How big should my calorie surplus be?
A modest surplus of around 10–20% above maintenance is enough to build muscle while limiting fat gain. This calculator uses about a 20% surplus. Bigger surpluses mostly add fat, not extra muscle.
How much protein do I need to build muscle?
Around 1.6–2.2g of protein per kg of bodyweight is the evidence-based range for muscle growth. The calculator sets protein to about 25% of your (higher) bulking calories, which lands most people in that range.
How fast can I gain muscle?
Realistically about 0.25–0.5 kg of bodyweight per month for non-beginners (beginners can gain faster). If you are gaining much quicker than that, a good chunk is likely fat — ease the surplus back.