Brix Pol Purity Calculator: How It Works

This calculator works out the purity of sugar cane or beet juice from two lab measurements: Brix (total dissolved solids percentage) and Pol (apparent sucrose percentage). You enter both values, and it returns the purity percentage, which is the ratio of Pol to Brix expressed as a percent. The result is a quick quality check used in sugar factories and mills to see how much of the dissolved solids is actually sucrose.

Formula

The formula is simple: Purity (%) = (Pol / Brix) × 100

• Pol – apparent sucrose content, measured in °Z (or % sucrose by weight). It comes from a polarimeter reading of the juice.
• Brix – total dissolved solids, measured in °Bx. It is usually read with a refractometer or hydrometer.
• Purity – the percentage of dissolved solids that are sucrose. It is unitless (a percentage).

Both inputs must be in the same units (percent). If your Brix is 18 and Pol is 15, purity is (15/18) × 100 = 83.33%.

Worked Example

Using the default values from the calculator:

1. Brix = 18%
2. Pol = 15%
3. Purity = (15 / 18) × 100 = 0.8333 × 100 = 83.33%

The calculator shows 83.33% as the headline result.

Why Purity Matters in Sugar Production

In a sugar mill, cane or beet is crushed to extract juice. That juice contains water, sucrose, and other dissolved solids like glucose, fructose, salts, and organic acids. Brix measures all of that dissolved material, while Pol measures only the sucrose (and a few optically active impurities that rotate light similarly). Purity tells you how “clean” the juice is – how much of the dissolved solids is actually sugar you can crystallize.

High purity (above 85%) means the juice is rich in sucrose and will crystallize well. Low purity (below 70%) means lots of impurities, which make crystallization harder and reduce yield. Factories monitor purity at every stage – from raw juice to syrup to molasses – to adjust boiling and centrifugation.

How to Read the Result

The purity percentage is a ratio, not a yield. A purity of 80% does not mean you will recover 80% of the sugar; it means 80% of the dissolved solids are sucrose. Actual recovery depends on evaporation, crystallization efficiency, and losses in molasses.

• Raw juice – typically 75–85% purity.
• Clarified juice – often 80–88% after liming and settling.
• Syrup – usually 85–92% after evaporation.
• Molasses – around 30–40% purity, where most impurities end up.

If the result is unexpectedly low, check your Brix and Pol readings – a common error is using a Brix reading from a hydrometer calibrated at a different temperature.

Common Mistakes and How to Avoid Them

Most errors come from measurement, not the formula itself.

• Temperature mismatch – Brix and Pol are temperature-dependent. Always measure both at the same reference temperature (usually 20°C). If not, apply correction factors.
• Unit mix-up – Pol is often given in °Z, which is essentially percent sucrose, but some labs report it as a decimal (0.15 instead of 15). Make sure both inputs are in percent.
• Using the wrong Brix – There are two Brix scales: true Brix (sucrose solution) and apparent Brix (refractometer reading of a complex solution). For purity, use the apparent Brix from your refractometer, not a hydrometer reading that may be affected by other solids.
• Rounding too early – If you round Pol to 15 and Brix to 18, you get 83.33%. But if the actual values are 15.4 and 18.2, the real purity is 84.6%. Keep one decimal place in your measurements.

Limitations of the Purity Formula

The simple ratio assumes that all optically active substances in the juice rotate light the same way as sucrose. In reality, other sugars (glucose, fructose) and some amino acids also rotate light, so Pol is an “apparent” sucrose value. For most factory control, this is accurate enough. But for research or precise trade calculations, you may need HPLC (high-performance liquid chromatography) to measure true sucrose.

Also, Brix from a refractometer is based on the refractive index of a pure sucrose solution. When other solids are present, the reading is slightly off. This is why purity is called “apparent purity” in many technical documents.

The formula also assumes both measurements are on the same juice sample. If you take Brix from one sample and Pol from another (e.g., different times or locations), the purity will be meaningless.

How to Choose a Brix Pol Purity Calculator

Any calculator that lets you enter Brix and Pol and divides them will give the same result – the math is trivial. What matters is the accuracy of your inputs and whether the calculator handles units correctly.

• Check that it accepts percent values (not decimals like 0.15).
• Check that it does not apply any hidden correction factors – unless you specifically want a temperature-corrected purity.
• If you need corrected purity (e.g., for official sugar quality reports), use a calculator that includes a temperature correction table, or do the correction manually first.

For most routine mill control, a simple ratio calculator like this one is all you need.

Frequently Asked Questions

What is the difference between Brix and Pol?

Brix measures all dissolved solids (sucrose plus impurities) as a percentage by weight, usually via refractometer. Pol measures only the sucrose (and optically similar substances) using a polarimeter. Purity is the ratio of Pol to Brix.

Can purity be above 100%?

In theory, no – Pol cannot exceed Brix because sucrose is part of the dissolved solids. But measurement errors (temperature, calibration) can produce values slightly above 100% in practice. If you see that, re-check your readings.

What is a good purity for cane juice?

For raw cane juice, 75–85% is typical. After clarification, it rises to 80–88%. If purity is below 70%, the cane may be immature, damaged, or the juice is stale.

Does temperature affect purity?

Yes. Both Brix and Pol change with temperature. Standard reference is 20°C. If your measurements are at a different temperature, apply corrections before calculating purity.

Is purity the same as sugar recovery?

No. Purity is the proportion of sucrose in dissolved solids. Recovery also depends on evaporation efficiency, crystallization, and losses in molasses. Purity is a quality indicator, not a yield prediction.

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in brix | Brix | % | 18 | 0
in pol | Pol | % | 15 | 0
out purity | Purity | % | (pol / brix) * 100 | 2