Not sure if any boy can 'forecast' how big his penis will be at full adult length, you would have to be very immaculate and precise in measuring your penis from age 11 onwards. So at 13 and a month old your penis is (I'll forget about it soft and concentrate on what it is erect) 5.1" and that was from about when you reached your 12th birthday when it was 3.1", SO it has grown 2", that's 2 inches in 1 year and still is growing. You 'are on the road' for it to be 8" by the full adult length, I am thinking that the word HOPE is in your mind because that 5.1" you are now might be as big as it's going to be, however, it could grow a little more but I doubt the two inches it gained when you were 13 will continue at that rate, IF it did your forecast of 8" will come during the year when you are 15, or at least 16 at the latest, the growth rate usually slows down a bit, more likely to 'top up' at a more respectable 6 or at the most 7" good luck.
Secondly, to the boy who says his soft penis is 7" and his hard erect penis is FOUR inches, haha, yesterday was the 1st of April.
Measure it from the base of your erection against the pubic bone but NOT stretched into your balls (testicles), hence the body side that does not extend into your testicles, I am sure most boys who say they have a 7" or longer penis are doing just that, extending your penis length into the testicles can add up to a much as two or more inches.
Read this again guys its official research that has been done into penis size for age and carries all the information you are all asking about!
Average Penis Length What is the average penis length?
There has never been an official investigation into the average penis length of adult men. Therefore the internet holds a wide variation of average lengths. The most common measurement (based on scientific research) is an average erect penis length of 5.5 inches (14cm), with the majority of penises somewhere between 5.3 inches (13.5 cm) and 6.3 inches (16 cm). Recent research about the average penis length shows that men from Stoke-on-Trent have the longest penis, and men from Bristol the biggest girth. It is hard to say what the real penis average in the UK is, because it really depends on the research.
What is the average flaccid penis length?
A flaccid penis measures about two-thirds the length of an erect penis.
The average flaccid penis length of a grown man is 3.9 inches (9.9 cm). How can I measure average penis length? If you would like to know how your penis compares to the average penis length you should measure from the pubic bone to the tip of the penis.
When does your penis stop growing?
Your penis will grow as you get older. But your penis only really starts growing when you hit puberty. Most of the growth takes place between the ages of 10 and 15 years old. Your penis stops growing when you’re about 20 years old.
Below you can see the average penis lengths in different age categories: Age - Average penis length.
12 years old - 2.8 to 4.1 inches (7.1 to 10.4 cm)
13 years old - 3.4 to 5.4 inches (8.6 to 13.7 cm)
14 years old - 3.9 to 5.7 inches (9.8 to 14.6 cm)
15 years old - 4.6 to 6 inches (11.8 to 15.3 cm)
16 years old - 4.9 to 6.2 inches (12.5 to 15.7 cm)
17 years old - 5.3 to 6.3 inches (13.5 to 15.9 cm)
18 years old - 5.4 to 6.3 inches (13.7 to 16 cm)
What is considered a small penis? An erect penis length of 4.3 to 7.9 inches (10.9 to 20 cm) is generally considered normal. An erect penis length of less than 3.9 inches (9.9 cm) only occurs in 1 out of 5.000 men. The smallest penis ever measured was 0.6 inch (1.5 cm). What is considered a large penis? An erect penis that is longer than 8.7 inches (22.1 cm) is considered a very large penis. According to surveys this only occurs in 1 out of 10.000 men.
The largest penis ever measured was 13 inches (33 cm). What is the average penis length in other countries? Africa boasts the largest average penis length. Surveys show that men in Congo and Ghana have the longest average penis length, with an average of about 7.1 inches (18 cm). In Europe the French men have on average the longest penis, followed by the Swedish and Estonian men. This is also the top three in regards to largest penis girth.
The small average penis length is found in Asia. South-Korea has the shortest average penis length, measuring 3.9 inches (9.9 cm). India and China are close behind.
you also need to learn how to measure length correctly as well what a lot don't seem to know!
Yet they still ask the same question time an time again rather than read official posts that tells them all they need to know.