Schnur Scale Calculator

Introduction

The Schnur Scale Calculator tells you how much breast tissue must be removed for a breast reduction to meet insurance rules. Many health plans use this scale to decide if surgery counts as medical care instead of cosmetic surgery.

The tool works in two steps. First, it uses your height and weight to find your Body Surface Area (BSA) with the Mosteller formula. Then it matches your BSA to the Schnur Sliding Scale table at the 22nd percentile. The result is the smallest number of grams that must be removed from each breast.

Just pick your units, enter your height and weight, and press Calculate. You will see your BSA, your minimum gram amount, a step-by-step solution, a chart, and the full reference table with your row marked.

This calculator gives an estimate only. Every insurance plan sets its own rules, so check with your surgeon and your plan before you make any decisions.

How to use our Schnur Scale Calculator

Enter your height and weight. The calculator finds your Body Surface Area (BSA) and shows the minimum grams of breast tissue per breast at the 22nd percentile of the Schnur Sliding Scale, plus a step-by-step solution and chart.

Unit System: Pick US / Imperial or Metric. This changes the height and weight fields, the sliders, and the results.

Height — ft: In US mode, type your height in whole feet, from 4 to 7.

Height — in: Type the leftover inches, from 0 to 11.9. For example, 5 ft 6 in.

Total height slider (inches): Drag the slider to set your full height in inches. The feet and inches boxes update as you drag.

Height (cm): In Metric mode, type your height in centimeters, from 120 to 220.

Height slider (centimeters): Drag to set your height in centimeters instead of typing it.

Weight: In US mode, type your weight, then choose lbs or st (stone). The range is 50 to 400 lbs.

Weight slider (pounds): Drag to set your weight in pounds. The weight box updates with it.

Weight (kg): In Metric mode, type your weight in kilograms, from 30 to 200.

Weight slider (kilograms): Drag to set your weight in kilograms.

Calculate: Click this button to see your BSA in m² and ft², your minimum gram amount per breast, and the math behind it.

Reset: Click this to clear your entries and start over with the default values.

What Is the Schnur Scale?

The Schnur Sliding Scale is a chart doctors and insurance companies use for breast reduction surgery. It links your body surface area (BSA) to the smallest amount of breast tissue a surgeon must remove from each breast. The amount is measured in grams. If the planned removal meets or beats that number, the surgery is more likely to be seen as medical, not cosmetic.

How Body Surface Area Fits In

Body surface area is an estimate of how much skin covers your body. It is found from your height and weight using the Mosteller formula:

BSA (m²) = √(height in cm × weight in kg ÷ 3600)

Bigger bodies have a larger BSA, so the scale asks for more tissue to be removed. A smaller BSA means a smaller gram target.

The 22nd Percentile

The Schnur scale came from a 1991 study by Dr. Paul Schnur. He looked at women who had breast reductions and compared how much tissue was removed. Cases at or above the 22nd percentile were mostly done for health reasons, like back pain, neck pain, shoulder grooves, and rashes. Cases below that line were mostly done for looks. That is why many insurance plans use the 22nd percentile as the cut-off.

Why People Use It

To see if a breast reduction may be covered by insurance.
To help plan surgery goals with a plastic surgeon.
To understand the paperwork before a pre-approval request.

Things to Keep in Mind

The scale runs from 1.35 m² to 2.55 m² of BSA. Numbers outside that range are not on the chart. Every insurance plan is different. Some use the Schnur scale, some use a flat gram amount (often 500 grams per breast), and some use other rules. Symptoms, photos, and notes from your doctor also matter.

This tool gives an estimate only. It is not medical advice and it is not a promise of coverage. Talk with a board-certified plastic surgeon and check your own health plan for the rules that apply to you.

Formulas used

Body Surface Area (Mosteller formula)

\text{BSA}\ (\text{m}^2) = \sqrt{\frac{\text{height}_{\text{cm}} \times \text{weight}_{\text{kg}}}{3600}}

BSA converted to square feet

\text{BSA}\ (\text{ft}^2) = \text{BSA}\ (\text{m}^2) \times 10.7639

Minimum grams per breast (linear interpolation on the Schnur scale)

g = g_1 + \frac{\text{BSA} - b_1}{b_2 - b_1} \times (g_2 - g_1)

Height conversion (feet and inches to centimeters)

\text{height}_{\text{cm}} = \left(\text{ft} \times 12 + \text{in}\right) \times 2.54

Weight conversion (pounds or stone to kilograms)

\text{weight}_{\text{kg}} = \text{lb} \times 0.453592 \quad\text{or}\quad \text{weight}_{\text{kg}} = \text{st} \times 6.35029

Frequently asked questions

What is a good BSA for breast reduction insurance approval?

There is no "good" or "bad" BSA. Your BSA just sets your gram target. A smaller BSA means a lower gram goal, and a larger BSA means a higher one. For example, a BSA of 1.60 m² needs about 310 grams per breast, while a BSA of 2.20 m² needs about 895 grams per breast.

How many grams is a cup size in breast reduction?

As a rough guide, removing about 200 to 300 grams from each breast drops you about one cup size. This varies a lot from person to person. Breast width, skin, and starting size all play a part. Your surgeon can give you a better estimate after an exam.

Does insurance require 500 grams for breast reduction?

Some plans do use a flat 500 grams per breast rule. Others use the Schnur Sliding Scale, which sets your target based on your body size. A few use a mix of both. Read your plan's medical policy for breast reduction, or ask your surgeon's insurance coordinator to check for you.

What happens if my surgeon removes less tissue than the Schnur scale requires?

The insurance company can deny the claim and leave you with the bill. That is why surgeons weigh the removed tissue during surgery and record it in the operative report. If your surgeon thinks a smaller removal is best for your body, talk about costs before the surgery date.

Can I get a breast reduction covered if I do not meet the Schnur scale?

Sometimes. Many plans will still approve surgery if you show strong symptoms and failed other treatments. Helpful proof includes notes about back, neck, and shoulder pain, shoulder grooves from bra straps, rashes under the breasts, photos, and records of physical therapy or pain medicine that did not help. You can also appeal a denial.

Who created the Schnur Sliding Scale?

Dr. Paul Schnur, a plastic surgeon at the Mayo Clinic, published the scale in 1991. He surveyed plastic surgeons about breast reduction cases and compared the grams removed to each patient's body surface area. Cases at or above the 22nd percentile were mostly done for health reasons, so that became the cut-off many insurers use today.

Does losing weight change my Schnur scale number?

Yes. Weight loss lowers your BSA, which lowers your gram target. Losing 20 pounds might drop your target by 50 to 100 grams. But weight loss can also shrink your breasts, so the amount your surgeon can remove may go down too. Some plans ask you to try weight loss first.

Is the Schnur scale based on total grams or grams per breast?

Grams per breast. If the scale says 523 grams, that means 523 grams from the left breast and 523 grams from the right. Some insurers add the two together and look at the total, but the standard Schnur table lists a per-breast number.

What is the Mosteller formula for body surface area?

The Mosteller formula is BSA in m² = the square root of (height in cm × weight in kg ÷ 3600). It is simple and widely used in medicine. For a person who is 168 cm and 77 kg, the math is √(168 × 77 ÷ 3600) = √3.593 = about 1.90 m².

Do both breasts need to have the same amount removed?

No. Breasts are often different sizes, so surgeons usually remove more from the larger one to even them out. Most insurers want each breast to meet or come close to the gram target, but some accept an average of the two. Ask your plan how it handles uneven removals.

How much does breast tissue weigh?

Breast tissue weighs about the same as water, so 500 grams is a little over one pound. A D cup breast often weighs around 500 to 700 grams. A very large breast can weigh well over 1,000 grams, which is more than two pounds on each side.

Does BMI matter for breast reduction approval?

Often yes, but it is a separate rule from the Schnur scale. Many surgeons and insurers set a BMI limit, commonly 30 to 40, because higher BMI raises the risk of wound healing problems. You may need to lower your BMI before the surgery is approved or scheduled.

How long does insurance pre-approval for breast reduction take?

Most plans answer within two to four weeks after they get the full request. Your surgeon sends photos, measurements, the planned gram amount, and notes on your symptoms and past treatments. Missing paperwork is the main cause of delays, so make sure your records of pain and failed treatments are included.

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