Anthropometrics

Anthropometrics are direct measurements of the human body.

They describe size, proportion, and shape using physical dimensions such as lengths, circumferences, and skinfold thickness — without relying on electrical signals or device-specific assumptions.

In Formetrix, anthropometrics form the foundation of body composition analysis.

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What Anthropometrics Are

Anthropometric measurements include:

• Lengths (e.g. height, limb length)

• Circumferences (e.g. waist, hip, limbs)

• Skinfolds (subcutaneous fat thickness at specific sites)

They capture real, physical change in the body — not estimates inferred from impedance or proprietary models.

Because they measure size directly, anthropometrics are:

• repeatable

• device-independent

• comparable over time

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How Formetrix Uses Anthropometrics

Formetrix treats anthropometrics as primary inputs. From them, the app:

• calculates composition metrics (e.g. body fat %, lean mass)

• derives interpretation indexes (e.g. ratios, symmetry)

• builds trends and cumulative views

• anchors AI-based interpretation in real measurements

No single measurement is assumed to be perfect. Meaning comes from how measurements evolve together over time.

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Measurement Points in the Interface

Each anthropometric measurement is represented visually on the body model.

Ripple Indicators

• Show the location of a measurement point

• Appear when points are collapsed

• Reduce visual clutter in View Mode

Measurement Lines & Circles

When expanded:

• Lines indicate linear measurements (e.g. limb length)

• Circles indicate circumferences (e.g. waist, thigh)

• The displayed value updates based on the active measurement selection — either a specific measurement date or the cumulative view

• Tapping the measurement again opens the historical chart for that specific measurement point, showing how it has changed over time

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Skinfold Measurements

Skinfolds measure subcutaneous fat thickness using calipers.

In Formetrix, skinfolds:

• are optional and advanced

• improve body fat estimation accuracy

• unlock higher-resolution composition metrics

However, they are technique-sensitive.

Important

Skinfolds improve accuracy only when measured correctly and consistently. Poor technique can reduce accuracy more than simpler methods.

Formetrix supports multiple validated skinfold methods (e.g. JP3, DW4, JP7) and clearly indicates when requirements are met.

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Grouping Anthropometric Measurements

Anthropometric measurements can be organized into groups based on purpose.

Defaults:

• General

  • Height, weight, waist circumference, hip circumference, chest circumference

• Body Building

  • Height, weight

  • Neck, chest, waist, hip

  • Left/right biceps, thighs, calves

• Symmetry

  • Left/right arm length

  • Left/right biceps and forearms

  • Left/right leg length, thighs, calves

• Skinfolds (SF)

  • Chest, biceps, abdominal

  • Triceps, thigh

  • Subscapular, suprailiac, midaxillary, calf

• All Except Skinfolds

  • All anthropometric points except skinfold sites

In Formetrix, groups:

• simplify input

• reduce unnecessary repetition

• allow goal-specific tracking

• keep the body model coherent

You can enable, disable, or customize these groups at any time via pointer presets.

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Measurement Points — Context & Notes (T-Pose)

Category	Measurement Point	What It Represents	Usage Notes / When It Matters
Basics	Height	Structural body length	Stable reference value. Required for most indexes. Does not need frequent re-measurement.
	Weight	Total body mass	Changes frequently. Core input for composition and interpretation.
	Shoulder Width	Skeletal width	Structural proportion reference. Useful for balance and visual analysis, not short-term change.
Head & Neck	Head Circumference	Cranial size	Rarely changes. Mostly informational.
	Neck Circumference	Upper torso girth	Required for tape-based body fat estimation (e.g. US Navy). Technique consistency is critical.
Torso	Chest Circumference	Upper torso volume	Useful for physique and posture tracking. Not required for core composition estimates.
	Waist Circumference	Primary abdominal reference	Most important waist point. Used by multiple health and composition indexes (WHtR, ABSI, VFA). Track consistently.
	One Inch Above Belly Button	Upper abdominal distribution	Optional. Useful to distinguish upper abdominal fat or bloating effects.
	One Inch Below Belly Button	Lower abdominal distribution	Optional. Often changes differently than upper waist during fat loss.
	Hip Circumference	Pelvic width	Required for waist-to-hip ratio and female tape-based body fat estimation.
Arms – Left / Right	Arm Length	Limb length	Structural measurement. Useful for symmetry and proportion, not frequent change tracking.
	Bicep Circumference	Upper arm size	Common in physique tracking. Track left/right for symmetry if relevant.
	Forearm Circumference	Lower arm size	Useful for strength or sport-specific tracking.
	Wrist Circumference	Joint size	Mostly structural. Rarely changes.
Legs – Left / Right	Leg Length	Limb length	Structural reference. Useful for symmetry and biomechanical context.
	Thigh Circumference	Upper leg size	Used for symmetry and visceral fat estimation. Landmark consistency matters.
	Knee Circumference	Joint size	Structural. Rarely changes.
	Calf Circumference	Lower leg size	Useful for symmetry and performance tracking.
	Ankle Circumference	Joint size	Structural reference.
Skinfolds (SF)	Chest, Triceps, Subscapular, Suprailiac, Abdominal, Thigh, Midaxillary, etc.	Subcutaneous fat thickness	Advanced use only. Improves body-fat accuracy only if technique is consistent. Poor technique reduces accuracy.