TDEE calculator bodybuilding guide: from maintenance to prep and off-season targets

The two phases at a glance

Both columns come from peer-reviewed reviews written specifically for natural bodybuilders. We read both abstracts on PubMed in September 2026.

Contest prep: Helms, Aragon & Fitschen, Journal of the International Society of Sports Nutrition, 2014. Off-season: Iraki, Fitschen, Espinar & Helms, Sports, 2019.

Why a bodybuilder's maintenance number needs extra care

The standard equations were built on the general population. Mifflin-St Jeor, the default in most calculators, estimates resting burn from weight, height, age and sex. It has no way of knowing whether 90 kg is mostly muscle or mostly fat, and muscle is the more metabolically expensive tissue. Mifflin's own 1990 paper found fat-free mass was the single best predictor of resting energy expenditure. For a lean, heavily muscled lifter, a weight-only formula therefore tends to read low.

The fix is to give the calculator your body fat percentage. It then uses Katch-McArdle, BMR = 370 + 21.6 × lean body mass (kg), which works from exactly the tissue that matters. The difference is not trivial. Take an 88 kg, 178 cm, 29-year-old man at 14% body fat. Mifflin gives about 1,853 kcal at rest. Katch-McArdle, using his 75.7 kg of lean mass, gives about 2,005 kcal. At a 1.725 multiplier that is 3,196 versus 3,458 kcal of daily maintenance, a gap of roughly 260 kcal a day.

Worked example: one lifter, both phases

Here are the published ranges applied to the 88 kg, 14% body fat lifter above, with maintenance taken as the Katch-McArdle estimate at 1.725 (about 3,460 kcal).

Calculated by TDEE Calculator Hub from the Helms (2014) and Iraki (2019) ranges, September 2026. The −20% starting point is this site's standard moderate cut. It is a first guess, not a figure from either paper; the papers set the rate, not the starting deficit.

Running contest prep off your TDEE

Helms and colleagues frame the prep target as a rate, not a calorie number: set intake at whatever produces a loss of about 0.5 to 1% of bodyweight per week, which they recommend to maximise muscle retention. That framing matters, because your maintenance will not stay still. As you get lighter, and as the body adapts to a long deficit, the calories that produced a 0.7% weekly loss in week two may produce almost nothing by week twelve.

So use the calculator once, at the start, to set a first target. From then on, the scale is the instrument. Weigh daily or near-daily under the same conditions, average each week, and compare the averages. If the loss is slower than 0.5% a week for two weeks running, trim intake a little. If it is faster than 1%, add a little back. Keep protein high throughout; 2.3–3.1 g per kg of lean mass is the review's range. Protein is the one number that doesn't come down as calories do.

The review also sets fat at 15–30% of calories, with the remainder from carbohydrate. It notes that meal timing and frequency appear to have little effect on fat loss or lean mass retention, beyond eating three to six meals with a solid protein dose around training.

Weekly rate targets by bodyweight

The percentages are easy to state and awkward to use. Here they are in kilograms per week, calculated from the published ranges.

Calculated by TDEE Calculator Hub, September 2026. Prep protein is set per kg of lean mass, so it depends on your body fat and isn't shown here. Use the worked example above as a template.

Setting up an off-season from your TDEE

Iraki and colleagues wrote their 2019 review because, as they put it, the off-season had received little scientific attention compared with dieting. Their recommendations translate into a simple setup:

1. Start from maintenance. Use the calculator with your body fat percentage, then confirm it against two weeks of stable weight if you can.
2. Add a 10–20% surplus. Novice and intermediate lifters can use the top of the range; advanced lifters should be more conservative with both surplus and rate of gain.
3. Target a gain of about 0.25–0.5% of bodyweight per week. For an 88 kg lifter that is roughly 0.2–0.4 kg a week, which can look like nothing on a single weigh-in. Judge it on weekly averages.
4. Set protein at 1.6–2.2 g per kg of bodyweight, split across three to six meals of about 0.40–0.55 g/kg each, including one within one to two hours of training.
5. Keep fat moderate at 0.5–1.5 g per kg and let carbohydrate fill the rest, at no less than 3–5 g per kg, so training quality doesn't suffer.
6. Re-check every four weeks. If waist measurements are climbing faster than lifts, the surplus is too big; if the scale hasn't moved in a month, it's too small.

Reading the scale without fooling yourself

Every recommendation on this page is a weekly rate, which makes the scale the most important tool you own. A single weigh-in is almost useless for this. Water, glycogen, salt, digestion and training soreness can move bodyweight by a kilogram or more overnight. That is larger than the whole weekly change you're trying to detect in an off-season.

The method that works is boring. Weigh at the same point every day, ideally first thing in the morning after using the bathroom and before eating. Write the number down, and at the end of each week take the average. Compare this week's average with last week's, never today's reading with yesterday's. Two weeks of averages moving in the wrong direction is a signal; one bad morning is noise.

Pair the scale with one or two other markers so you can tell muscle from fat. A tape measurement at the navel once a week, progress photos in the same light every two weeks, and your working weights on the main lifts are enough. If the scale is rising on schedule in the off-season but your waist is growing faster than your lifts, the surplus is too big. If your weight is falling on schedule during prep but your lifts are collapsing, the deficit may be too aggressive, or protein too low.

Where the calculator ends and coaching begins

A calculator is good at one thing: giving you a defensible first number in thirty seconds. It is not good at the things that decide a bodybuilding phase — noticing that your appetite, sleep or training performance is sliding, spotting that your weight stalled because you started walking less, or telling you when a deficit has run long enough and it's time for a diet break or to move back to maintenance.

Use the calculator for the starting point, the published ranges for the rules, and your weekly averages for the adjustments. If you're preparing for a show, the reviews cited here are worth reading in full — both are open access. For the underlying formulas, see our Mifflin-St Jeor and Katch-McArdle pages; for the general muscle-gain side, the lean bulk calorie calculator goes deeper on surplus sizing.