Early Roman historians estimated that the Colosseum could contain up to 87,000 people, according to sources. According to current estimates, this figure is closer to 50,000. The seats at the Colosseum were constructed in tiers to mirror the old Roman order. Men were allocated the upper tier and women were given the lower. The modern estimate is based on research done by John Coates in the 19th century. He found evidence of 20,924 hand-made bricks used in building the structure. In 1877, he calculated that the average size of a brick was 4 inches by 7 inches, which would make the total mass of the Colosseum about 22 million bricks (the actual weight is more than double this amount). Coates also noted that the structure was built within one year. This means that nearly half a million bricks must have been used in its construction. It is estimated that there were only about 100,000 people living in Rome at the time so this shows how many people had access to the games. There are actually several different estimates for the number of people who have attended a game in the Colosseum. Some say it is possible that up to three quarters of Rome's population could fit into the arena. But others say this is an overestimate and that only around 15,000 people can really be crammed in there.