The Common Atlantic octopus can grow to reach 10' or 3m in length when the body and arms are measured together. The giant Pacific octopus can reach lengths of 16' or 5m when the body and arms are measured together. The red octopus normally not exceeding 10 cm. The Blue-ringed octopus it has a body length of about 5cm, an arm length of about 10cm. The Day octopus can grow to around 30 or 76cm when the body plus arm length is measured. The Reef octopus have a body that grows up to 12cm in length and arms that can reach around 60cm. The Atlantic Longarm octopus has arms are commonly around 30cm in length whereas the body is only about 6cm.