The Science of Body Proportions: WHR, TPR and BBI Explained

6 min read·Published 2026-04-02·NB Medical Team

Key Takeaways

◎A WHR of 0.70 is the golden ratio for the most balanced female silhouette
◎The ideal TPR is 1.12 — this ratio produces the most natural lower-body line
◎A BBI of 85+ indicates ideal full-body balance; fine-tuning can elevate results further

Why Proportion — Not Weight

Body shape is not defined by weight alone. Two people at the same weight can have completely different silhouettes depending on the waist-to-hip ratio and thigh distribution. NB Body Design focuses on proportion rather than absolute measurements. A proportion-based approach directly informs surgical planning — it allows us to predict precisely which area to refine and by how much to achieve the most natural result.

WHR — Waist-Hip Ratio

WHR (Waist-Hip Ratio) divides waist circumference by hip circumference and is the most fundamental body proportion indicator. Research consistently identifies 0.70 as the most aesthetically and physiologically ideal value for women. In the NB scoring system, a WHR that deviates from 0.70 in either direction reduces the score. A value above 0.70 suggests a relatively wider waist; below 0.70 suggests relatively underdeveloped hips.

WHR

Ideal WHR

0.70

TPR — Thigh Proportion Ratio

TPR (Thigh Proportion Ratio) is calculated by doubling one thigh circumference and dividing by the hip circumference. The ideal TPR is 1.12, at which the thigh-to-hip transition appears most fluid and natural. A TPR above 1.12 indicates thighs that are proportionally larger relative to the hips; below 1.12 the thighs may appear slender but disconnected from the hip line.

TPR

Ideal TPR

1.12

ALR — Arm Line Ratio

ALR (Arm Line Ratio) multiplies one upper-arm circumference by 3.5 and divides by the hip circumference. The ideal is 1.00, at which the arm line harmonises with the overall body proportion. The arm line is often overlooked, but when ALR falls outside the ideal range it affects the entire silhouette when wearing clothes.

Refining just the arm line can completely transform the perception of shoulder width and upper-body proportion.

BBI — Body Balance Index

BBI (Body Balance Index) is the average of WHR, TPR and ALR scores, each converted to a 0–100 scale. A BBI of 85 or above represents ideal full-body balance. BBI does not hide individual deficits. Even if a high WHR score elevates the average, a low TPR keeps the overall BBI below the ideal threshold — ensuring the index reflects true whole-body balance rather than partial optimisation.

BBI

Ideal BBI

85+

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