Body Recomposition Calculator
Lose fat and add lean mass at the same time, and the scale stops being useful. This calculator finds the daily intake where the two cancel out — the recomposition point — then gives you the protein target and the month-by-month body fat projection that go with it.
Estimated TDEE is 2,735 kcal, and at your training tier the lean mass you can add is worth 81 kcal/day of fat loss. Eat 2,654 and the two cancel: body fat falls, body weight holds.
You entered 2,400 kcal, a deficit of 335 kcal/day. Deeper than the recomposition window. Fat loss outruns the lean mass you can build, so body weight drops. That is a cut, and a cut works — it just is not recomposition.
Protein 115 g/day at 1.8 g per kg of your 63.9 kg lean mass. Fat 64 g, carbohydrate 341 g.
At your intake: fat −1.32 kg/month, lean +0.32 kg/month, net weight −1.01 kg/month. Projected body fat: 15.6% at 3 months, 10.9% at 6 months, 0.1% at 12 months.
Recomposition window for your tier: 43–119 kcal/day below TDEE, which is 1.5661836331797665 to 4.3 percent of your daily expenditure.
What body recomposition actually means
Recomposition is a period during which fat mass falls and lean mass rises at the same time. Body weight is the sum of the two, so when the rates are close the scale does nothing for months while your body fat percentage moves steadily downward. That is the whole appeal, and it is also the whole problem: the scale, which is the easiest thing to measure, is exactly the instrument that stops reporting anything.
The way out is to stop trying to read the outcome off a scale and start planning with rates instead. If you know two numbers — how fast fat is leaving, and how fast lean mass can arrive — everything else follows: what to eat, how much protein, how long the target takes, and which part of your result came from which process. That is what the rest of this page computes.
The two inputs are wildly unequal in size. A modest 300 kcal daily deficit removes about 1.19 kg of fat a month. A trained lifter might add 0.32 kg of lean mass in that same month. Fat loss is the big lever on body fat percentage; lean gain is the small one. The tables below put a number on how small, because the honest answer is smaller than most recomposition marketing implies.
Computed: the recomposition point, and how narrow the window is
Set monthly fat loss equal to monthly lean gain and solve for the deficit. That deficit is the recomposition point: eat there and weight is flat while body fat falls. Around it sits a band where the scale drifts by less than 0.15 kg a month — invisible on a bathroom scale, which is what makes it feel like recomposition. Both tables use a 178 cm, 30-year-old, moderately active man at 80 kg and 20 percent body fat, and a 165 cm, 30-year-old woman at 65 kg and 28 percent.
The striking part is the width. For a lifter with one to three years of training, the entire recomposition window is 43 to 119 kcal a day — roughly one slice of bread, or 1.6 to 4.3 percent of daily expenditure. Nobody tracks intake to that precision in free-living conditions, which is worth saying plainly: recomposition is not a target you hit by arithmetic. It is a zone you operate inside by eating close to maintenance, hitting a protein target, and training hard enough to justify the lean gain rate you assumed.
The other reading of the same table is more encouraging. Because the window is defined by how much lean mass you can add, and that is nearly fixed, the practical instruction is not "find the perfect deficit" but "get your deficit small enough that it stops dominating". Below about 150 kcal a day, the recomposition story and the cut story are the same story with different emphasis.
Computed: what a daily deficit actually removes
This is the one table on this page with no modelling assumptions in it at all beyond the 7700 kcal constant. Pick a deficit, divide by the energy value of fat, and you have a rate.
Read it against the lean gain column of the previous table. A 300 kcal deficit removes 1.19 kg of fat a month while a trained lifter adds 0.32 kg of lean — the fat side is nearly four times larger. At 100 kcal the ratio is about 1.6 to one. That crossover is why small deficits are where recomposition lives and large deficits are just cuts.
Computed: twelve months at the recomposition point
Same 80 kg man at 20 percent body fat, trained one to three years, eating 75 kcal a day below his estimated 2,740 kcal TDEE — the recomposition point for his tier, rounded to the nearest 25. Fat mass falls 0.296 kg a month, lean mass rises 0.320 kg a month.
Four and a half percentage points of body fat in a year, during which the scale moved 0.28 kg — about the weight of a large apple, and well inside normal day-to-day water variation. Anyone weighing themselves weekly through this year would conclude nothing was happening. The tape measure and the body fat estimate would both disagree, and they would be right.
Note also that the rate is not constant in percentage terms even though the kilogram rates are fixed: the first month costs 0.38 percentage points, the twelfth costs 0.37, but the percentage base is shrinking, so each point gets slightly harder to buy. On the body fat percentage chart this is the difference between moving within a band and crossing into the next one.
Computed: the same twelve months, tier by tier
Each tier is run at its own recomposition point, rounded to the nearest 25 kcal. This is the table that shows what training history is actually worth in a recomposition plan.
Two things are worth pulling out. First, the beginner's advantage is enormous: the same twelve months buys 8.97 percentage points for a first-year lifter and 1.56 for someone with three-plus years of training, purely because the lean gain rate differs by a factor of five. Second, the bottom row of each table is the honest control group — with no progressive resistance training there is almost no lean gain to cancel the deficit, so the year is just a very slow cut with a nearly flat scale.
Some rows land below the essential-fat bands shown on our body fat percentage chart. Those rows are arithmetic, not targets. The model subtracts fat at a constant rate and has no floor.
Computed: how much of the drop is muscle, really
Run the six-month projection twice more — once with the fat loss but no lean gain, once with the lean gain but no fat loss — and you can split the body fat percentage change into the part that came from losing fat and the part that came from adding lean mass.
This is the most useful number on the page for calibrating expectations. Even at the recomposition point, where the deficit is as small as it can be while still removing fat, only about a fifth of the six-month improvement comes from added lean mass. Push the deficit to 300 kcal and lean gain contributes under six percent. Muscle gain is real and it is worth training for, but as a driver of the body fat percentage number over six months it is a rounding error next to the fat you did not eat.
Computed: what one percentage point costs
Divide a month by the first month's change in body fat percentage and you get the calendar price of a point. The net weight column is the other half of the trade: the faster you buy points, the more the scale has to move.
A useful planning shortcut falls out of this: at a deficit of about 200 kcal a day you lose one body fat percentage point roughly every five weeks while losing less than half a kilogram a month on the scale. That combination — visible progress, nearly invisible scale movement — is the practical version of recomposition for most trained people.
Protein: the one number that is not negotiable
Calorie arithmetic decides how fast fat leaves. Protein is what makes the lean side of the ledger possible at all, and it is the part of a recomposition plan you can actually control day to day. The table is pure multiplication — the target in grams per kilogram of lean body mass times your lean mass. Note that lean mass, not body weight, is the reference: two people at 80 kg with different body fat percentages need different amounts, and using total weight over-prescribes for the one carrying more fat.
Where does the rest of the plate go? Fat has a floor set by your own choice — 0.8 g per kilogram of body weight is the default in the calculator above — and carbohydrate takes whatever is left. For the 80 kg man with 64 kg of lean mass, at 1.8 g/kg of protein:
Protein holds absolutely still across that whole range — 115 g whether you eat 2,100 or 2,900 calories. Carbohydrate absorbs the entire difference. That is the structural reason a recomposition plan is mostly a protein target plus a modest calorie adjustment: the macro that matters does not move when you change the deficit, so you can change the deficit without rebuilding the whole diet.
Computed: how long your fat stores can fund the deficit
A deficit is a withdrawal from a finite account. This table is that arithmetic run forward, with the last column expressed against the 16 kg of fat mass our 80 kg example man starts with — a useful sanity check on any long plan.
The rows that exceed 100 percent are not predictions, they are a demonstration that the constant rate has to stop. In reality metabolism adapts, intake drifts, and nobody holds a 700 kcal deficit for a year. The practical use of this table is short-horizon: over three months the numbers are plausible, and they tell you that a 300 kcal deficit consumes roughly a fifth of a lean-ish person's entire fat mass in that time.
How to run this in practice
- Get a starting body fat number before you start. The entire plan is built on lean mass, so a wrong starting percentage propagates into every number below. Use the Navy tape method or our body fat calculator, and take the measurement twice.
- Set protein first, calories second. Protein is fixed by your lean mass and does not change when you adjust the deficit. Lock it, then move calories.
- Pick a deficit below 200 kcal a day. Per the rate table, that band keeps the scale nearly flat while still buying a percentage point every five weeks or so.
- Weigh daily, read weekly. Daily weight is too noisy to interpret at these rates; the weekly average is the signal. Our weight loss percentage tool exists because percentage change is more comparable than kilograms across people.
- Re-measure body composition every four weeks, not weekly. The changes are smaller than the error of any cheap method, so more frequent measurement buys noise. See the error bar on our body fat percentage calculator.
- Recalibrate intake against the trend every three to four weeks. If the weekly average has not moved in a month and neither has body fat, you are at maintenance regardless of what the TDEE estimate said.
- Train with progressive overload. The lean gain rates that make recomposition possible assume the stimulus exists. Without it, use the bottom row of the tier tables.
Where this model is weak
- The lean gain rates are modelling parameters, not measurements. They are chosen to make the tables internally consistent and to separate the tiers by roughly the right magnitude. No figure on this page is a study result.
- Lean gain is held constant regardless of deficit. In reality a large deficit suppresses it, so the aggressive rows in the rate table overstate lean gain and understate how much of your loss is lean tissue.
- TDEE is an estimate from a prediction equation. Mifflin–St Jeor has error for any individual, and the activity multiplier is a coarse category. A 100 kcal error in TDEE is the same size as the entire recomposition window.
- There is no adaptive thermogenesis. The model does not shrink expenditure as you lose weight, so long projections run optimistic.
- There is no fat-mass floor. Rows that project below the essential-fat bands are arithmetic, not targets.
- Body fat percentage carries measurement error. If your starting estimate is three points off, the trajectory is shifted, though the rates are still right.
Frequently asked questions
What is body recomposition?
Losing fat and gaining lean mass over the same period, so body fat percentage falls while body weight stays roughly constant. The tables above show that at the point where the scale is perfectly flat, body fat still drops about 4.5 percentage points in a year for a trained lifter.
How many calories should I eat to recomp?
Under this model, maintenance minus the energy equivalent of the lean mass you can add — for a trained lifter that works out to roughly 43 to 119 kcal a day below TDEE. The calculator above computes it for your own numbers, and the button under the inputs sets your intake to it directly.
How much protein do I need for body recomposition?
The calculator defaults to 1.8 g per kilogram of lean body mass and lets you choose between 1.6 and 2.2. For the 80 kg example with 64 kg of lean mass, that is 115 g a day. Use lean mass rather than body weight as the reference so the number tracks the tissue it is meant to support.
How fast can you recomposition?
In this model, a trained lifter at the recomposition point drops one body fat percentage point every 2.7 months; at a 200 kcal deficit it is about one point every five weeks with the scale moving less than half a kilogram a month. A first-year lifter can go roughly twice as fast because the lean gain rate is larger.
Is recomposition better than bulking and cutting?
The tables give a fair answer: recomposition is slower in absolute body fat terms than a dedicated cut, and slower in lean mass terms than a dedicated bulk. What it buys is avoiding the fat gain of a bulk and the muscle risk of an aggressive cut. It suits people already near a body fat level they are happy to hold.
Can beginners really gain muscle while losing fat?
Yes, and the tier table quantifies why: the lean gain rate for a first-year lifter is five times the rate for someone with three-plus years of training, which makes the recomposition window five times wider and far easier to land inside by accident.
Why is my weight not changing but my body fat is?
Because fat mass and lean mass are moving in opposite directions at similar rates. At the recomposition point the net change is about 0.02 kg a month — far below the day-to-day water variation that dominates any single weigh-in.
Why does the scale barely move in the projections?
That is the definition of the recomposition point: the deficit is set so monthly fat loss equals monthly lean gain. Over twelve months the scale moves 0.28 kg in the worked example while body fat falls from 20.0 to 15.5 percent.
Do I need to track macros or only calories?
Protein is the macro that matters here and it does not change when you adjust your deficit, so a protein target plus total calories covers most of the benefit. Carbohydrate is whatever is left after protein and fat, as the split table above shows.
How do I know if it is working?
Weekly average body weight that is flat or drifting slightly, plus a body fat estimate that falls when re-measured every four weeks. If neither moves after a month, you are at maintenance regardless of the estimate, and intake needs to come down.
Where do the 7700 kcal and lean gain numbers come from?
7700 kcal per kilogram is the energy value this page assigns to body fat, used as a modelling constant. The lean gain rates by training tier are parameters chosen by this calculator so the tables are internally consistent. Neither is presented as a measured result, and the limits section lists what that means for accuracy.
Related tools
TDEE calculator · body fat calculator · body fat percentage with error bar · Navy body fat calculator · weight loss percentage · body fat percentage chart · FFMI calculator
Not medical advice. This page runs an explicit arithmetic model whose assumptions are listed above; it is not a prediction of your outcome and not a substitute for professional advice. Speak to a qualified professional before making significant changes to your diet or training. See our disclaimer.