Size guide — how the system works

This page explains how Opera Campi suggests sizes. There are two methods: one based on body measurements in cm, and one based on weight and height ratio. The measurement method is more accurate and takes priority when the customer knows their measurements. The weight/height method is used when only weight and height are available.

Always select the table matching the product's fit: female products use the Female garment table and the Female allowances; male products use the Male garment table and the Male allowances. For unisex products, ask the customer which fit they prefer before choosing. The same body measurements produce different sizes on the two tables.

Method 1 — Body measurements

These tables show the sample garment measurements (in cm) for each size. These are the measurements of the finished garment, not the body. To find the right size, take the customer's body measurement, add the allowance percentage shown in the allowance table below, and find the first size whose garment measurement equals or exceeds that value.

Formula: body measurement × (1 + allowance) ≤ garment measurement → that is the correct size.

Example (male): chest = 92 cm, allowance = 7% → 92 × 1.07 = 98.44 cm → first size with chest ≥ 98.44 is S (100 cm) → suggest S.

Example (female): chest = 90 cm, allowance = 6% → 90 × 1.06 = 95.40 cm → first size with chest ≥ 95.40 is XS (96 cm) → suggest XS.

Which measurements apply to which garment

Do not mix upper-body and lower-body measurements. Using hips to size a sweater is the most common cause of an oversized suggestion.

Garment type	Measurements used	Measurements ignored
Tops: sweaters, t-shirts, shirts, polos, jackets	Chest (deciding), Shoulders (check only)	Waist, Hips, Thigh
Bottoms: trousers, shorts, leggings	Waist, Hips, Thigh	Chest, Shoulders
Full-body: overalls, one-piece	Chest, Waist, Hips, Thigh	Shoulders

Garment measurements — Female

Chest and Shoulders come from the female top block. Waist, Hips, Thigh, Hem and Inseam come from the female trouser block. Note that female hips and thigh are wider than the male block at the same nominal size — never size a female product against the male table.

Size	Chest (cm)	Shoulders (cm)	Waist (cm)	Hips (cm)	Thigh (cm)	Hem (cm)	Inseam (cm)
XXS	92	39	72	96	60	25.5	78
XS	96	40	76	100	62	26.5	78
S	100	41	80	104	64	27.5	78
M	104	42	84	108	67	29	78
L	108	43	88	112	70	30.5	78
XL	112	44	92	116	73	32	78
XXL	116	45	96	120	76	33.5	78
XXXL	120	46	100	124	79	35	78

 

Garment measurements — Male

Size	Chest (cm)	Shoulders (cm)	Waist (cm)	Hips (cm)	Thigh (cm)
XXS	92	39	72	93	55
XS	96	40	76	97	57
S	100	41	80	101	59
M	104	42	84	105	61
L	108	43	88	109	63
XL	112	44	92	113	65
XXL	116	45	96	117	67
XXXL	120	46	100	120	69

Allowance table

Always add the allowance percentage to the customer's body measurement before comparing with the garment table. The allowance accounts for ease of movement and for the intended fit of the block. It is normally positive; the only exception is the male waist, which is slightly negative (−1%) because the male trouser block is designed to sit just below the natural waist.

Measurement	Male allowance	Female allowance
Chest	7% (0.07)	6% (0.06)
Shoulders	1% (0.01)	1% (0.01)
Waist	-1% (-0.01)	0% (0.00)
Hips	5.5% (0.055)	1.5% (0.015)
Thigh	5% (0.05)	5% (0.05)

When multiple measurements within the same scope are provided, always take the largest suggested size across them. The size is determined by the most constraining measurement.

Example: chest suggests M, waist suggests L on a full-body garment → suggest L.

Shoulders — how to measure and when to use

Shoulders are a check measurement, never the deciding one. Measure straight across the back from the tip of one shoulder to the tip of the other, following the line of the shoulder seam of a well-fitting garment. Do not measure around the shoulders, over the arms, or diagonally: these give values 4 to 6 cm higher and will push the suggestion up by two or three sizes.

Override rule: if the size suggested by shoulders is more than one size away from the size suggested by chest, discard the shoulder result and use chest. Mention to the customer that the shoulder figure looks inconsistent and ask how it was taken.

Knitwear tolerance

On knitwear (filato), if a body measurement exceeds the garment measurement by less than 1.5 cm after the allowance is applied, that size still fits and remains valid. This tolerance does not apply to woven fabric (tessuto).

Method 2 — Weight and height ratio

When the customer does not know their body measurements in cm, use weight (kg) divided by height (cm) to calculate a ratio. Compare the ratio with the threshold table below to find the suggested size. Use the Male table for male products, the Female table for female products. For unisex products, ask the customer which fit they prefer before choosing the table.

Formula: ratio = weight ÷ height. Example: 70 kg ÷ 180 cm = 0.389 → M (male).

Ratio thresholds — Male

Size	Ratio range	Example body	Notes
XXXS	≤ 0.265	44 kg / 166 cm	No real data, cautionary value
XXS	0.265 – 0.295	50 kg / 170 cm	No real data, cautionary value
XS	0.295 – 0.335	57 kg / 170 cm	Sparse data in dataset
S	0.335 – 0.380	62–69 kg / 180 cm	P95 from real orders ✓
M	0.380 – 0.444	70–80 kg / 180 cm	P95 from real orders ✓
L	0.444 – 0.480	80–87 kg / 182 cm	P95 from real orders ✓
XL	0.480 – 0.516	87–95 kg / 185 cm	P95 from real orders ✓
XXL	0.516 – 0.625	95–115 kg / 183 cm	P95 from real orders ✓
XXXL	> 0.625	110+ kg / 177 cm	P95 from real orders ✓

Ratio thresholds — Female

Size	Ratio range	Example body	Notes
XXXS	≤ 0.255	40 kg / 157 cm	No real data, cautionary value
XXS	0.255 – 0.290	42–48 kg / 158 cm	P95 from real orders ✓
XS	0.290 – 0.331	50–53 kg / 166 cm	P95 from real orders ✓
S	0.331 – 0.390	53–65 kg / 167 cm	P95 from real orders ✓
M	0.390 – 0.430	60–70 kg / 169 cm	P95 from real orders ✓
L	0.430 – 0.468	68–75 kg / 170 cm	Sparse data, interpolated
XL	0.468 – 0.526	75–95 kg / 174 cm	P95 from real orders ✓
XXL	0.526 – 0.546	110–120 kg / 190 cm	P95 from real orders ✓
XXXL	> 0.546	above XXL	Interpolated

Practical examples — Male

Height (cm)	Weight (kg)	Ratio	Suggested size
180	62	0.344	S
180	69	0.383	S
180	70	0.389	M
175	75	0.429	M
182	82	0.451	L
185	90	0.486	XL
183	100	0.546	XXL
176	110	0.625	XXXL

Practical examples — Female

Height (cm)	Weight (kg)	Ratio	Suggested size
158	42	0.266	XXS
166	53	0.319	XS
167	57	0.341	S
168	65	0.387	S
170	70	0.412	M
172	65	0.378	S
176	80	0.455	L
174	82	0.471	XL

Worked examples — Method 1, Female

Garment	Body measurements	Calculation	Result
Sweater (top)	Chest 88	88 × 1.06 = 93.28 → first chest ≥ 93.28 is XS (96)	XS, decided by chest
Sweater (top)	Chest 90	90 × 1.06 = 95.40 → first chest ≥ 95.40 is XS (96)	XS, decided by chest
Trousers (bottom)	Waist 73, hips 102, thigh 60	waist 73.00 → XS (76); hips 103.53 → S (104); thigh 63.00 → S (64)	S, decided by hips and thigh

Rules and edge cases

Method priority: if the customer provides body measurements in cm, always use Method 1. The weight/height ratio is a fallback only.

Correct block: before applying Method 1, confirm whether the product uses the female or the male block. Applying female measurements to the male table under-calls hips and thigh by roughly one full size.

Scope of measurements: use only the measurements listed for that garment type in the scope table above. Never let hips or thigh decide the size of a top.

S/M borderline (male): for a 180 cm man, the S/M boundary is at approximately 69–70 kg. A difference of 1 kg changes the size. If the customer is unsure, suggest M for a relaxed fit and S for a closer fit.

Products starting from S: if the product does not carry XXXS, XXS or XS, the system skips those thresholds and assigns the smallest available size. A customer with ratio 0.320 on an S-to-XXL product will receive S.

Unisex products: always ask whether the customer wants a male or female fit before choosing the table. The same person will receive different size suggestions depending on the answer.

Made to measure: if the customer's ratio is below 0.265 (male) or 0.255 (female), or if their body measurements fall significantly outside the table range, suggest the made-to-measure option rather than forcing an extreme size.

Material and fit: knitwear (filato) has natural stretch and is more forgiving at borderline sizes; apply the 1.5 cm tolerance described above. Woven fabric (tessuto) follows the thresholds strictly. When in doubt on a woven garment, suggest the larger size.

Multiple measurements conflict: when different body measurements within the same scope point to different sizes, always go with the largest suggested size. Never average them.

Calibration status: the female allowances are calibrated on a small sample. Chest at 6% is validated on two confirmed cases; hips at 1.5% and thigh at 5% rest on a single confirmed trouser case and should be re-checked as more confirmed fits are collected. Treat borderline female trouser suggestions with extra care and offer the exchange option proactively.

Further assistance: if you are doubtful, you can suggest the user to write at casa@operacampi.pro or to chat through the other chat in the bottom right of the webpage to talk directly with one of the team of Opera Campi.

How to respond to size questions

If the customer provides weight and height: calculate the ratio (weight ÷ height), use the correct table based on sex or product type, state the suggested size.

If the customer provides body measurements in cm: identify the garment type, select the female or male block, apply the allowance to the measurements in scope, compare with the garment table, and return the first size that fits all of them. Always state which measurement was the deciding factor.

If the customer provides neither: ask for at least weight and height. Do not guess a size based on general descriptions like "average build" or "medium frame".

If the customer is between two sizes: ask whether they prefer a relaxed or close fit, then recommend accordingly. Never leave the customer without a clear recommendation.

If the customer gives the measurements of another garment, you don't need to add margin. The margin needs to be added only to body measures.

If the customer asks for the product measurements, each product has a Shopify "product type" field containing the product category. This is linked to a page named "Size" followed by the product type, where the product measurements can be found. For example, if the product type is "Maglietta1", the product measurements will be available on the Shopify page "Size Maglietta1".