These values are estimates and trend measures, not a medical diagnosis. Do not measure over injured, irritated, or scarred skin. If you are unsure, in pain, or have an implanted active medical device, follow the manufacturer’s guidance or seek medical advice.
01 / SKINFOLDS
Technique matters more than the number.
Choose an equation first and measure only the sites it asks for. A clean, repeatable procedure is more useful than collecting as many sites as possible.
- Locate and mark the site. Use the stated bony landmarks and distance; measure on the same mark when you repeat the session.
- Lift the skinfold. Use thumb and index finger to lift a small, stable double layer of skin and subcutaneous fat away from muscle—do not squeeze it or pull only the skin tip.
- Place the jaws. Centre the caliper jaws across the fold, about 1 cm below your holding fingers and in the same direction as the fold. Keep holding the fold.
- Press to the click and read. With a manually operated caliper that has a “Press” point, apply steady thumb pressure until the pressure limiter clicks or engages. Read the scale, then release the fold. Do not squeeze further after the click.
Before every session
- Whenever possible, use the same measurer, body side and sequence each time. Many protocols specify the right side; follow the protocol for your chosen equation.
- Keep skin dry, clean, and at normal temperature; do not measure immediately after training, a hot bath, sauna, or sun exposure.
- Stand relaxed in your normal posture and do not tense up for the measurement.
How hard should you press?
For a caliper with a manual “Press” point, the click is your consistent end point: press slowly and evenly until the pressure limiter engages, then read the scale. Do not stop before the click or continue squeezing after it. There is no additional target gap; comparable readings come from using the same click point every time.
This guidance applies to this pressure-limiter design. A simple plastic caliper can still be useful for your own trend, but its readings should not be compared directly with a different caliper design or a professional assessment.
Repeat & record
- Measure every site at least twice. If readings differ by more than 2 mm, take a third and average the closest two.
- Do not compress one site repeatedly in a row: take one reading at every site, then return for the repeat.
- With this design, read at the click point. If your specific method prescribes a different reading interval, apply that interval consistently and do not mix rules.
02 / SITES
The nine skinfold sites in the calculator.
For measurement, use the bony landmarks, fold direction, and protocol description.
Diagonal
Pectoral
Only use this site when the selected equation requires it: follow the line between the anterior axillary fold and nipple. For men, the site is approximately halfway along that line; for women, about one third of the way from the armpit. The equation's exact protocol takes priority.
Vertical
Abdominal
About 2 cm to the right of the navel. Keep the abdomen relaxed—do not draw it in, brace, or hold your breath.
Vertical
Thigh
On the anterior midline of the thigh, halfway between the inguinal crease and the top edge of the kneecap. Shift weight to the other leg and keep the measured leg relaxed.
Vertical
Triceps
At the centre of the back of the relaxed upper arm, exactly midway between the shoulder landmark (acromion) and the elbow tip (olecranon).
Diagonal
Suprailiac
Immediately above the palpable top of the iliac crest. The fold follows its natural downward diagonal. Some equations specify an anterior versus mid-axillary line—follow the equation you use.
Vertical
Midaxillary
On the side of the torso on a vertical line through the middle of the armpit, level with the bottom of the sternum (xiphoid). Raise the arm briefly to mark it, then let it hang relaxed to measure.
Diagonal
Subscapular
1–2 cm below the inferior angle of the shoulder blade. The fold travels down and outward at roughly 45°. Keep shoulder and arm relaxed.
Vertical
Biceps
On the front of the upper arm over the middle of the biceps, at the same height as the triceps site. Let the arm hang and turn the palm forward.
Vertical
Calf
On the medial calf at its maximum circumference. Place the foot on a low step, flex the knee to about 90°, and mark the site; this makes the fold easier to lift cleanly.
Vertical
Lower back
On the lower back; pinch parallel to the spine and follow the exact position specified by your Parrillo protocol.
03 / SCALE
Scale: weight is direct; BIA needs context.
Weight is measured directly by a stable scale. A body-fat scale’s percentage is a BIA estimate and is strongly affected by fluid distribution, food, training, and temperature.
Body weight
- Put the scale on a hard, level floor—not carpet. Use the same scale whenever possible.
- Measure in the morning after using the toilet, before breakfast and training, barefoot or in the same light clothing.
- Stand still in the centre. If the scale visibly varies, measure two or three times and record the stable value.
Body-fat scale (BIA)
- Use the same scale, user profile and time of day whenever possible. Make sure the profile has your correct height, age and sex.
- Measure under similar conditions each time. Avoid comparing readings taken just after hard exercise, a sauna, substantial alcohol intake or a large meal, or while you have a fever or diarrhoea. Keep your feet clean and dry, and stand still during the measurement.
- Use BIA body-fat readings to follow trends, not as exact measurements. If you have an active implanted medical device or another contraindication, follow the scale manufacturer’s instructions.
04 / CIRCUMFERENCES & LENGTHS
Keep tape tension, position and landmarks consistent.
For comparable measurements, apply the tape the same way each time. Keep it level and perpendicular to the body, use consistent tension, and find the same anatomical landmarks at every session.
Standard flexible tape
- Use a non-stretch tailor’s tape. Lay it flat: no twists, no sagging, and no digging into the skin.
- For circumferences, bring it fully around the body, align the endpoint with zero, and read at normal exhalation. The tape touches the skin without compressing it.
- Use the same posture, site, and tape tension every time. Do not move a marked site by eye at the next session.
Retractable body tape
- Put the loop around the site and tighten only until the defined click or manufacturer marker. Do not pull the tape further after that.
- Hold the case and viewing window in place without pressing them into the body. Make sure the zero point is seated correctly in the case.
- Use the same tape for comparable sessions. The click creates repeatable tension, but it does not replace the correct measurement height.
| Calculator value | Measurement location | Keep consistent |
|---|---|---|
| Chest | Horizontal around the fullest part of the chest. | Arms relaxed; read after a normal exhalation. |
| Waist | Horizontal midway between the lowest rib and the top of the iliac crest. | Do not draw in the abdomen. Keep this definition for WHR/WHtR every time. |
| Hip | Horizontal around the widest extension of the buttocks/hips. | Distribute weight evenly; do not measure over pockets or clothing. |
| Upper arm right / left | Midway between the shoulder landmark and elbow tip. | Arm hangs relaxed; do not pump or flex. |
| Thigh right / left | Midway between the inguinal crease and the top of the kneecap. | Stand upright with even weight; use mirrored sites on both sides. |
| Calf right / left | Maximum circumference of the calf. | Find and mark the highest point once; keep both feet flat. |
| Arm length | Recommended tracking value: from the shoulder landmark (acromion) to the bony wrist landmark. | Let the arm hang; do not measure to the fingertip or use a garment’s inseam. |
| Leg length | Recommended tracking value: from the palpable lateral hip landmark (trochanter) to the outer ankle bone. | Measure barefoot, upright, and with another person’s help. Do not mix this with inseam or trouser length. |
For consistent tracking, record your measurement routine during your first session—for example, measuring in the morning after using the bathroom, taking waist measurements at the midpoint, and measuring skinfolds on the right side. This makes it easier to repeat the same conditions at future sessions.