Plato to SG Calculator and Conversion Chart

If you have ever brewed from a European recipe or used a commercial brewing system, you have probably run into Degrees Plato and wondered how it lines up with the specific gravity numbers you are used to. This calculator converts Plato to SG and SG back to Plato instantly. Below the calculator, you will find the full conversion chart, the formulas behind the numbers, and what those Plato readings actually mean for your beer.

What Is Degrees Plato and Where Did It Come From?

Degrees Plato (°P) is a unit that tells you the sugar concentration in wort as a percentage by weight. A reading of 12°P means that 12 grams out of every 100 grams of wort is dissolved sugar.

The scale is named after Fritz Plato, a German scientist who refined an earlier measurement system in the late 19th century. Before Plato, brewers used the Balling scale, developed by Karl Balling in the 1840s. Fritz Plato and his team at the German Imperial Normal Aichungs Commission revised Balling’s work with more precise measurements, and the updated scale took his name.

Continental European breweries adopted Degrees Plato as their standard. It gave brewers a direct read on sugar content rather than a density comparison to water. That directness is why commercial brewers still prefer it today.

Plato vs Specific Gravity: What Is the Difference?

Both measurements describe how much sugar is dissolved in your wort. They just express it differently.

• Specific Gravity (SG) compares the density of your wort to the density of pure water. Water sits at 1.000. Wort with dissolved sugars sits above that, typically between 1.030 and 1.120, depending on how much grain went into the recipe.
  
• Degrees Plato (°P) skips the density comparison and goes straight to the sugar content. It tells you the percentage of sucrose by weight in the solution.
• The two are not interchangeable by a simple ratio, but they describe the same physical reality. A wort at 12°P and a wort at 1.048 SG are the same liquid. The difference is only in how that liquid is being described.
• One practical difference: SG readings feel more intuitive to homebrewers because the numbers change clearly during fermentation. Plato uses smaller values that take familiarity. This is why American homebrewers prefer SG, while European and professional brewers use Plato.

There are two ways to convert Plato to SG. Which one you use depends on how much accuracy you need.

Quick Approximation Formula

For fast field estimates, multiply Plato by 0.004 and add 1.000.

SG = 1.000 + (°P × 0.004)

Example: 15°P × 0.004 = 0.060, so SG = 1.060

This works well enough for rough calculations and quick mental math. At lower Plato values, it is reasonably accurate. As you get into higher gravity territory above 20°P, the approximation starts to drift from the true value.

Precise Polynomial Formula

For accurate brewing calculations, the industry standard formula is:

SG = 1 + (°P / (258.6 − ((°P / 258.2) × 227.1)))

The constants 258.6, 258.2, and 227.1 come from empirical brewing research that mapped the relationship between sugar concentration and liquid density across a wide range of wort samples. This nonlinear formula captures the curve in that relationship that the simple approximation misses.

Example: 15°P using the polynomial formula gives SG = 1.0611, while the quick formula gives 1.060. At lower Plato values, the difference is small. At 25°P the quick formula gives 1.100 while the polynomial gives 1.1057. The gap widens at higher gravities, which matters for high-gravity brewing.

SG to Plato Formula

To convert in the other direction, from SG to Plato, the formula is:

°P = 135.997 × SG³ − 630.272 × SG² + 1111.14 × SG − 616.868

Example: SG 1.048 °P = 135.997(1.048³) − 630.272(1.048²) + 1111.14(1.048) − 616.868 = 11.9°P

An alternative formula used by some calculators: °P = (−463.37) + (668.72 × SG) − (205.35 × SG²)

Both formulas give results that are close enough for brewing purposes. The first (cubic polynomial) is the more widely cited standard.

Complete Plato to SG Conversion Chart (0.5°P to 40°P)

Plato (°P)	SG
0.5	1.002
1.0	1.004
1.5	1.006
2.0	1.008
2.5	1.010
3.0	1.012
3.5	1.014
4.0	1.016
4.5	1.018
5.0	1.020
5.5	1.022
6.0	1.024
6.5	1.026
7.0	1.028
7.5	1.030
8.0	1.032
8.5	1.034
9.0	1.036
9.5	1.038
10.0	1.040
10.5	1.042
11.0	1.044
11.5	1.046
12.0	1.048
12.5	1.050
13.0	1.053
13.5	1.055
14.0	1.057
14.5	1.059
15.0	1.061
15.5	1.063
16.0	1.065
16.5	1.068
17.0	1.070
17.5	1.072
18.0	1.074
18.5	1.076
19.0	1.079
19.5	1.081
20.0	1.083
20.5	1.085
21.0	1.087
21.5	1.090
22.0	1.092
22.5	1.094
23.0	1.096
23.5	1.099
24.0	1.101
24.5	1.103
25.0	1.108
25.5	1.106
26.0	1.108
26.5	1.113
27.0	1.115
27.5	1.117
28.0	1.120
28.5	1.122
29.0	1.124
29.5	1.127
30.0	1.129
30.5	1.132
31.0	1.134
31.5	1.136
32.0	1.139
32.5	1.141
33.0	1.144
33.5	1.146
34.0	1.149
34.5	1.151
35.0	1.154
35.5	1.156
36.0	1.159
36.5	1.161
37.0	1.164
37.5	1.166
38.0	1.169
38.5	1.171
39.0	1.174
39.5	1.176
40.0	1.179

Specific Plato Values Explained in Context

The conversion chart gives you numbers. This section tells you what those numbers mean for actual beer.

7°P to SG (1.028)

A wort at 7°P is a light, low-gravity wort. It sits at the starting point for session beers and light lagers. German Schankbier and some traditional British milds are brewed in this range. The low sugar content means the finished beer will be well below 4% ABV. At 7°P you are not building a strong beer. You are building something drinkable, low in alcohol, and easy on the palate.

10°P to SG (1.040)

10°P is the entry point for what most people picture when they think of standard everyday beer. American lagers, light ales, and session IPAs often start here. The finished beer typically comes in around 4 to 4.5% ABV, assuming normal attenuation. Most commercial light beers are brewed at or just below this Plato value.

12°P to SG (1.048)

12°P is where a lot of the world’s most popular beers sit. German Helles, Czech Pilsner, and many English pale ales are designed around this original gravity. The Czechs actually call this strength “dvanáctka“, the twelve, and it represents the standard strength reference point in Czech brewing culture. At 12°P you are looking at roughly 5% ABV in the finished beer.

13°P to SG (1.053)

13°P sits between standard and full-bodied. American craft pale ales, amber ales, and many session IPAs target this range. It gives the brewer enough malt backbone to support hop additions without pushing into strong beer territory. Finished ABV typically lands around 5.5 to 6%.

15°P to SG (1.061)

15°P marks the start of what most brewing systems classify as a stronger beer. American IPAs, German Export lagers, and many Belgian ales are brewed at this gravity. At 15°P with good attenuation, the finished beer reaches roughly 6.5 to 7% ABV. This is also the Plato range where recipe precision starts to matter more because small measurement errors have a larger effect on the final alcohol content.

20°P to SG (1.083)

This is where high-gravity brewing begins. Double IPAs, Belgian Tripels, and strong ales are brewed in this range, finishing around 10 to 11% ABV with full attenuation. This is also the point where the quick approximation formula loses accuracy. At 20°P, the quick formula gives 1.080 while the polynomial gives 1.083. From here upward, the polynomial formula is the one to use.

High-gravity brewing above 20°P brings extra challenges. Yeast stress increases at higher sugar concentrations, and the simple approximation formula becomes less reliable. The polynomial formula and precise measurement tools matter more at these gravity levels.

Walk into any commercial brewery in Germany, the Czech Republic, or Belgium, and you will not hear anyone talking about 1.048 gravity. They say 12 Plato. The reasons go back further than most people realize, and they are practical, not just traditional.

Commercial brewers prefer Plato because it gives them direct, actionable numbers at every stage of production:

A brewer who works only in SG and converts to Plato only when required is adding unnecessary steps and potential for error into a process where precision matters. That is why most commercial brewing software, including BeerSmith and ProMash, supports both units, but European and international operations default to Plato as the working standard.

This is where Plato becomes more than just a conversational curiosity. If your brewing system gives you gravity readings in Plato rather than SG, you can calculate ABV directly from those Plato readings without converting to SG first.

Original Plato and Final Plato

Just like SG-based brewing uses Original Gravity (OG) and Final Gravity (FG), Plato-based brewing uses Original Plato (OG°P) and Final Plato (FG°P).

Original Plato is the sugar concentration of the wort before fermentation begins. Final Plato is the reading taken after fermentation is complete, when yeast has consumed most of the fermentable sugars.

The drop from Original Plato to Final Plato represents how much sugar was consumed. Most well-attenuated ales finish at 2 to 3°P. Lagers and highly attenuated styles can finish below 2°P.

Plato to ABV Formula

The standard formula used by commercial brewers to calculate ABV from Plato readings is:

ABV = (OG°P − FG°P) × 0.59 / (1 − (FG°P / 258.6))

For most practical purposes, a simpler approximation works well:

ABV ≈ (OG°P − FG°P) × 0.6

Example: OG = 12°P, FG = 2.5°P ABV ≈ (12 − 2.5) × 0.6 = 9.5 × 0.6 = 5.7% ABV

The 0.6 factor accounts for the relationship between sugar consumption and ethanol production. It is less accurate at extreme gravities but reliable across the normal brewing range of 8°P to 20°P original gravity.

For higher accuracy, convert your Plato readings to SG using the polynomial formula and then use the standard SG-based ABV calculation.

Brewers sometimes adjust alcohol content. Every gravity reading, whether in Plato or SG, is only accurate when taken at the right temperature. Hydrometers are calibrated at a standard temperature, typically 20°C (68°F). Refractometers have their own calibration standard.
When your wort sample is warmer than the calibration temperature, it is less dense than it would be at the standard temperature. The hydrometer sits higher than it should, giving you a falsely low reading. When the sample is cooler, the opposite happens.
Temperature variation of just 5 to 10°F can shift a hydrometer reading by 0.001 to 0.002 SG units. In Plato’s terms, that can mean a difference of 0.25 to 0.5°P. For a recipe targeting 12°P exactly, that is a meaningful error.
The correction works like this: Corrected SG = Measured SG + (0.000132 × (T − Tcal))
Where T is your sample temperature, and Tcal is the hydrometer’s calibration temperature.
Most digital refractometers include automatic temperature compensation (ATC) for readings at room temperature. For wort samples taken directly from a hot kettle, letting the sample cool in a tube before measuring gives a more accurate result than applying a correction factor manually.

Here is something that catches a lot of brewers off guard. A refractometer reads Plato or Brix by measuring how light bends through the liquid. Before fermentation, the only dissolved substance bending that light is sugar. After fermentation begins, alcohol is also present, and alcohol bends light differently than sugar does.

This means a refractometer reading taken from fermenting or fermented beer is no longer an accurate measure of sugar concentration. The alcohol in the solution pulls the reading down, making it appear that more sugar has been consumed than actually has.

If you take a refractometer reading mid-fermentation and use it as your Final Plato without correction, your calculated ABV will be wrong. The correction formula for post-fermentation refractometer readings in Plato:

Corrected FG°P = 1.0000 − 0.0044993 × (OG°P) + 0.011774 × (Apparent FG°P)

For final gravity confirmation after fermentation, a hydrometer remains the most reliable tool. It measures density directly and is not affected by alcohol interference in the same way a refractometer is.

Plato in Regulatory and Commercial Brewing

Plato is not just a measurement preference in commercial brewing. In many countries, it carries legal weight.

In Germany, the Stammwürze printed on a beer label is the original wort concentration in Plato. This number is used to calculate the tax owed on the beer at production. German beer law ties the Stammwürze to the beer’s character and style classification. A beer labeled as a 12°P Pilsner must actually have been brewed from a 12°P wort.

In the United States, the TTB requires breweries to document original gravity for excise tax purposes. While TTB documentation typically uses SG, many larger American craft breweries that produce at scale or export to European markets maintain parallel documentation in Plato for cross-market consistency.

For craft breweries that sell internationally or enter European competitions, understanding Plato is not optional. European competition entries, import documentation, and quality certificates from European labs all work in Plato. A brewer who only knows SG and has to convert everything is adding unnecessary steps and potential for error.