It’s axiomatic that men lie about the size of their penis. There are numerous alleged rules that exist to help one discover a man’s true penis size, ranging from using his shoe size, to the distance between the tips of his thumb and forefinger at their most distant points, to simply modifying whatever he tells you to a suitably smaller value. I have access to data from a Dutch study on penis size that examined 1783 men. The most useful thing about these observations is that only was actual penis size recorded, but so was self-reported penis size. That meant that a formula could be constructed to convert self-reported penis size into a likely actual penis size.

For accuracy, I sought to minimize the root mean square error, that is, the square root of the average squared value of the difference between the actual penis size and my formula’s estimate. I used Microsoft Excel, specifically, its solver function, in order to handle the mathematics. I considered three types of possible formulas. If we let y equal the estimated penis size and x equal the self-reported penis size, the three formulas were:

y=Ax

y=x+B

y=Ax+B

I considered linear formulas the upper limit of competent mental complexity, and so restricted myself to the above. Since the data also included ethnicity, I solved both for everyone and by ethnicity. Except for y=Ax+B, though, the values didn’t change much between ethnicities. Self-reported penis size was provided in centimeters, while actual penis size was measured more accurately, to the nearest tenth of a centimeter.

As mentioned, there were 1783 men in total. The breakdown by ethnicity is below.

Ethnicity |
Count |

Arab | 125 |

Australoid | 4 |

Black | 78 |

Caucasian | 1124 |

Central Asian | 12 |

East Asian | 105 |

Indian | 23 |

Latino (multiracial) | 144 |

Mediterranean | 90 |

Mixed race | 78 |

Total | 1783 |

For the formula y=Ax, the ideal formula is to multiply self-reported penis size by 0.85 to arrive at the estimator of the actual penis size. Even when I broke the data down by ethnicity, the value of A varied only from 0.84 to 0.86. For example, a self-reported penis size of 15 cm would be converted to 15 cm * 0.85 = 12.75 cm. The values by ethnicity are reproduced below. I was surprised how little difference there was. And the round number makes it a simple math equation, as well. Simply remove 15%!

y=Ax |
A |

Overall | 0.85 |

Arab | 0.84 |

Australoid | 0.85 |

Black | 0.84 |

Caucasian | 0.85 |

Central Asian | 0.86 |

East Asian | 0.85 |

Indian | 0.85 |

Latino (multiracial) | 0.84 |

Mediterranean | 0.84 |

Mixed race | 0.86 |

For the formula y=x+B, the ideal formula is to remove 2.65 cm from the reported penis size to arrive at the estimator of the actual penis size, or for my American readers, a little over an inch (2.54 cm). This value varied more by race, but less than I would have supposed, going from a minimum of 2.35 for those of Mixed Race to a maximum of 2.74 cm for Arab men. (Australoid had a value of 2.92 cm, but only four samples, and so I have discounted it here.) It would be interesting to attempt to discern why the difference, or whether it’s statistically significant. It is intriguing that “macho” cultures, e.g. Arabs, Mediterraneans, and Latinos, have a larger difference between self-reported and actual penis size. For example, a self-reported penis size of 15 cm would be converted to 15 cm – 2.65 cm = 12.35 cm. The values by ethnicity are reproduced below. All values for B are in centimeters.

y=x+B |
B (cm) |

Overall | -2.65 |

Arab | -2.74 |

Australoid | -2.92 |

Black | -2.71 |

Caucasian | -2.65 |

Central Asian | -2.48 |

East Asian | -2.57 |

Indian | -2.51 |

Latino (multiracial) | -2.67 |

Mediterranean | -2.72 |

Mixed race | -2.35 |

For the formula y=Ax+B, the ideal formula is y = 0.66*x – 3.37 cm. These values fluctuated the most between ethnicities, but again, there was a strong pattern. For example, a self-reported penis size of 15 cm would be converted to (0.66 * 15 cm) + 3.37 cm = 13.27 cm. The values by ethnicity for A and B are reproduced below. All values for B are in centimeters. Unfortunately, these equations are rather more difficult than the previous two, and might require one to take out a calculator. Or, if you’re the entrepreneurial sort, perhaps you ought to create a statistically sound Penis Estimation App. You have my blessing.

y=Ax+B |
A |
B (cm) |

Overall | 0.66 | 3.37 |

Arab | 0.64 | 3.73 |

Australoid | 0.88 | -0.72 |

Black | 0.69 | 2.73 |

Caucasian | 0.65 | 3.58 |

Central Asian | 0.34 | 10.00 |

East Asian | 0.77 | 1.46 |

Indian | 0.53 | 5.64 |

Latino (multiracial) | 0.69 | 2.80 |

Mediterranean | 0.72 | 2.18 |

Mixed race | 0.65 | 3.73 |

And since I’m certain there’s interest, here’s the average penis size by ethnicity, in cm. Have I ever mentioned, by the way, my Central Asian heritage?

Ethnicity |
Average Penis Size (cm) |

Overall | 15.1 |

Arab | 15.3 |

Australoid | 15.8 |

Black | 15.1 |

Caucasian | 14.9 |

Central Asian | 17.5 |

East Asian | 14.6 |

Indian | 15.8 |

Latino (multiracial) | 15.2 |

Mediterranean | 14.7 |

Mixed race | 15.0 |

Now obviously, these formulas are far from perfect, and are only intended to provide a rough guide to estimating penis size, but I wish you the best of luck with them. Enjoy!

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