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Schnur Scale Calculator for Breast Reduction Insurance
The Schnur scale is a chart that relates body surface area (BSA) to the grams of breast tissue removed per breast in a reduction. Insurers commonly use its 22nd percentile line as a coverage threshold. A woman with a BSA of 1.80 m² sits at 441 g per breast on that line; at 2.00 m² it is 628 g. Enter height and weight below to read your own lines.
Prepared by Prospyr · Reviewed October 3, 2026 · Free, no sign-up, runs in your browser
Your height and weight
There is no consensus on which BSA formula to use, and the choice moves the result. Check which one your payer names.
Enter grams of tissue per breast, not both breasts combined, to see where it falls against the two lines.
Schnur 22nd percentile line (per breast)
509g
Body surface area
1.88 m²
5th percentile line
325 g
Between two table rows, so the grams are interpolated. Payers usually round to the nearest printed row.
A math aid based on a 1991 survey study. It does not say whether surgery is covered or needed. Insurers set their own criteria, and the surgeon decides what is right for the patient.
Full Schnur sliding scale table
Grams of breast tissue resected per breast. The row nearest your BSA is highlighted.
| BSA (m²) | 5th percentile (g) | 22nd percentile (g) |
|---|---|---|
| 1.35 | 127 | 199 |
| 1.40 | 139 | 218 |
| 1.45 | 152 | 238 |
| 1.50 | 166 | 260 |
| 1.55 | 181 | 284 |
| 1.60 | 198 | 310 |
| 1.65 | 216 | 338 |
| 1.70 | 236 | 370 |
| 1.75 | 258 | 404 |
| 1.80 | 282 | 441 |
| 1.85 | 308 | 482 |
| 1.90 | 336 | 527 |
| 1.95 | 367 | 575 |
| 2.00 | 401 | 628 |
| 2.05 | 439 | 687 |
| 2.10 | 479 | 750 |
| 2.15 | 523 | 819 |
| 2.20 | 572 | 895 |
| 2.25 | 625 | 978 |
| 2.30 | 682 | 1,068 |
| 2.35 | 745 | 1,167 |
| 2.40 | 814 | 1,275 |
| 2.45 | 890 | 1,393 |
| 2.50 | 972 | 1,522 |
| 2.55 | 1,062 | 1,662 |
Schnur scale calculator: how to read the result
You get three numbers: your BSA, the 22nd percentile line, and the 5th percentile line, both in grams of tissue per breast. If you also enter a planned resection weight, the tool places it against both lines.
- Below the 5th percentile line. In the 1991 study, surgeons called cases this small cosmetic.
- Between the lines. Mixed reasons. Policies that follow the scale usually review these individually.
- At or above the 22nd percentile line. The surgeons in the study called these cases medically necessary. This is the line most payers use.
The tool reads the table exactly at the printed BSA rows (1.35 to 2.55 m², steps of 0.05). Between rows it interpolates, because the columns grow roughly exponentially. Many payers round BSA to the nearest row instead, so ask which they do.
Worked example: Schnur sliding scale for a 170 cm, 70 kg patient
- Mosteller BSA = √(170 × 70 ÷ 3,600) = √3.306 = 1.82 m².
- The table has 441 g (22nd) and 282 g (5th) at 1.80 m², and 482 g and 308 g at 1.85 m².
- At 1.82 m² the interpolated lines are about 455 g (22nd) and 291 g (5th) per breast.
The BSA formula matters. For the same patient, Du Bois gives 1.81 m² (449 g) and the formula printed in Cigna's policy gives 1.83 m² (462 g). Rounding to the nearest printed row, 1.80 m² gives 441 g. Differences this size are normal; they are why you should match the payer's method.
Schnur scale and breast reduction insurance
The scale was built at payers' request. Schnur et al. surveyed 200 plastic surgeons, and 92 replied with height, weight and tissue removed for their last 15 to 20 reductions, plus whether each was cosmetic or medically necessary. Payer policies summarize the result as the 5th and 22nd percentile cutpoints.
A 2023 review of insurer policies in Plastic and Reconstructive Surgery Global Open found 85.7% of those reviewed used the Schnur sliding scale, generally with the 22nd percentile as the threshold, but with variations in the tables, in how the 5th to 22nd band is handled, and in other requirements. Some policies also set a flat minimum regardless of BSA (Cigna's policy lists more than 1 kg per breast). Insurers set their own criteria, so use this tool for orientation, not as a coverage answer.
The scale also has critics. The survey relied on surgeons' recall and their own cosmetic versus medical labels, and published commentary notes the original conclusions have been stretched by payers. It describes how a group of surgeons classified past cases. It does not measure symptoms or outcomes.
For plastic surgery practices
Preauthorization for breast reduction is paperwork-heavy: height, weight, BSA, planned and actual resection weight, symptom history and photos. Keep those numbers in the chart where the whole team can find them. Prospyr's charting and digital intake collect measurements and history before the consult, and the plastic surgery practice page shows how the front desk and surgical schedule fit together. For the BMI side of the same consult, see the BMI calculator for plastic surgery.
Frequently asked questions
What is the Schnur scale?
The Schnur scale, also called the Schnur sliding scale, is a table that pairs body surface area with a cutoff weight of breast tissue removed per breast. It comes from a 1991 paper in Annals of Plastic Surgery by Schnur and colleagues. Insurers adopted it to separate reconstructive from cosmetic breast reductions.
How is the Schnur scale calculated?
First calculate body surface area from height and weight, for example with the Mosteller formula: the square root of height in cm times weight in kg, divided by 3,600. Then read the grams per breast from the table at that BSA, in the 5th percentile or 22nd percentile column. The tool does both steps and interpolates between printed rows.
What does the 22nd percentile mean on the Schnur scale?
In the 1991 survey, surgeons classified their own past cases as cosmetic or medically necessary. The 22nd percentile line was the weight above which cases were reported as done for medical reasons. Most payers use it as their threshold, and some policies say resections between the 5th and 22nd lines are reviewed case by case.
Does a breast reduction qualify for insurance if it meets the Schnur scale?
Not automatically. A published review of payer policies found they vary in how they apply the scale and in what else they require, such as symptoms, photos and failed conservative treatment. Meeting the scale is one criterion at most. Check the plan's own medical policy and ask the surgeon's office to submit the preauthorization.
Which body surface area formula does the Schnur scale use?
Insurer policies print the table but there is no consensus on which BSA formula to pair it with. Some name their own, and the formulas differ by a few hundredths of a square meter, which can move the result by 10 to 30 grams. This tool defaults to Mosteller and lets you switch to Du Bois or the formula in Cigna's published policy.
Is the Schnur scale per breast or for both breasts?
It is per breast. The 1991 survey asked surgeons for the tissue removed from each breast, and payer policies state the table as grams per breast. If the pathology report gives a combined weight, divide it by two, or use the average of the two sides, before comparing.
Are there other ways to estimate breast resection weight?
Yes. Cigna's policy names the Descamps formula, which estimates resection volume from a regression on measurements. Whatever method is used, the number is a prediction until the specimen is weighed. In a 2018 study of 323 patients, 19% had a predicted resection of 500 g or more per breast but an actual weight below 500 g.
Sources and scope
- Schnur PL, Hoehn JG, Ilstrup DM, Cahoy MJ, Chu CP. Reduction mammaplasty: cosmetic or reconstructive procedure? Ann Plast Surg 1991;27(3):232-237 (PMID 1952749)
The original study behind the sliding scale.
- Cigna Medical Coverage Policy 0152: Reduction Mammoplasty for Macromastia (effective 11/15/2025), Appendix A
Source of the 5th and 22nd percentile table values used here, the per-breast framing, the BSA formula option and the 1 kg rule.
- Premera Blue Cross Medical Policy 7.01.503: Reduction Mammaplasty for Breast-Related Symptoms
Reproduces the 22nd percentile column (matches Cigna) and describes the survey method: 92 of 200 surgeons, last 15 to 20 cases.
- Blue Cross Blue Shield of Tennessee: The Schnur Sliding Scale chart
Published 22nd percentile column, used to cross-check the table.
- Boyd CJ et al. Preauthorization Inconsistencies Prevail in Reduction Mammaplasty. Plast Reconstr Surg Glob Open 2023 (PMC10602495)
Review of insurer policies: how many use the scale and how they vary.
- Kung TA et al. Accuracy of Predicted Resection Weights in Breast Reduction Surgery. Plast Reconstr Surg Glob Open 2018 (PMC6157938)
Describes the Schnur scale and its methodological criticisms. Predicted versus actual resection weights in 323 patients.
- Mosteller RD. Simplified calculation of body-surface area. N Engl J Med 1987;317:1098 (PMID 3657876)
The default BSA formula.
A math aid and reference, not medical or insurance advice. Insurers set their own coverage criteria and the surgeon decides what is appropriate for each patient. This tool does not say whether surgery is covered or needed.