Learn · Comp prep

How to predict your stage weight, months out

By Levi Hurst · 2026-10-10

Fat loss is far more predictable than most people think. If you know roughly how much lean mass you're carrying and roughly how lean you need to be on stage, you can estimate your stage weight months before the show, then track against it every week.

Step 1: Work out your lean mass

Lean mass is everything that isn't fat. Take your current bodyweight and remove your estimated body fat.

Lean mass = bodyweight × (1 − current body fat %)

Step 2: Pick a stage body fat

As a rough guide, women tend to compete somewhere around 12–15% body fat and men around 5–8%. Treat these as ranges, not targets to the decimal. Every body fat method has a real margin of error.

Step 3: Divide, don't multiply

If you keep your lean mass through prep, which is the whole point of training hard and dieting at a sensible rate, your stage weight is your lean mass divided by the fraction of you that will be lean on stage.

Stage weight = lean mass ÷ (1 − stage body fat %)

This is the step people get wrong. Multiplying your current bodyweight by (1 − stage body fat) doesn't give you a stage weight. It gives you your lean mass as if you were already at that body fat, which you aren't.

A real example: Ruby's prep

Ruby started her prep at 72kg and an estimated 24% body fat. That's about 54.7kg of lean mass (72 × 0.76).

• At 12% on stage: 54.7 ÷ 0.88 = 62.2kg
• At 15% on stage: 54.7 ÷ 0.85 = 64.4kg
• Predicted stage weight: 62.2–64.4kg
• Actual stage weight: 63.2kg

She landed inside the range we mapped out. Not because the formula is magic, but because she followed the plan and we tracked her weight every single day.

Why the prediction holds up

• Keep your lean mass. Heavy, high-quality training keeps the mechanical tension that tells your body to hold on to muscle while calories come down.
• Lose at a sensible rate. For most natural athletes that's roughly 0.5–1% of bodyweight per week. Faster than that and you start losing muscle, which breaks the maths.
• Track daily, adjust weekly. Daily weigh-ins averaged across the week cut through water noise. Decisions get made on the trend, not on one scary morning.

The prediction also tells you when to start. Divide the weight you need to lose by a realistic weekly rate and you have the length of your prep. Count back from show day, add a buffer, and that's your start date.

Want your stage weight mapped out for you? See comp prep coaching