Natural limit calculator

The two models

Casey Butt (2009)

Butt fitted a formula to the measurements of pre-steroid-era bodybuilders and modern natural competitors. Maximum lean mass = height^1.5 × (√wrist ÷ 22.667 + √ankle ÷ 17.01) × (body fat ÷ 224 + 1), all in inches and pounds. Bone structure — wrist and ankle circumference — does most of the work, which is why two people of the same height can have very different ceilings.

Berkhan's rule

Martin Berkhan's shortcut: stage weight in kilograms ≈ height in centimetres minus 100, at about 5–6% body fat. It is a rule of thumb for contest-ready naturals, so it reads lower than a Casey Butt result at 10% body fat.

What to do with the number

• If you are far below it, a lean bulk or a patient recomp has the most upside. See lean bulk and body recomp.
• If you are close to it, the remaining change is conditioning — compare 10% body fat with 8%.
• Either way, the ceiling takes a decade of consistent work. The 1 year and 3 year previews are the realistic milestones.

See it instead of estimating it

The formulas give you a weight. LiftLooks gives you the picture: the Genetic maximum transformation renders your natural ceiling on your own photo, keeping your face, frame, and lighting. It is the most shared result in the app for exactly that reason.