What age do babies usually crawl by?

[2pt4WiseMen]

DS is 9, nearly 10 months.
He can sit up really well (since 7 months) but cannot roll from his front to back yet and cannot crawl.
He gets incredibly frustrated as he leans forward when sitting down, falls onto his tummy and just cant get anywhere.
I'm hoping he will get the strength to lift himslelf up and move soon as then he might be happier!!
He likes standing on his feet if I hold his hands but cant work out to move his feet to do 'walking' either.

My ds didn't crawl til he was 10months, some babies don't crawl at all. He might just start walking. My ds used to rock from side to side on his bum to get places. I wouldn't worry too much

my ds crawled at about 9.5 months, and then walked at 10.5 months. Was always much happier stood up! He used to get so frustrated, but just wouldn't move not even roll! Oh and my son sat up really early by 5 months....so i thought he would crawl really early.

Some babies never crawl, my oldest nephew started walking about 11 months and then learnt to crawl afterwards.

DS never crawled, he bum shuffled from about 9 months, stood At 11\mths and walked at about 13 months. Then he crawled!

Neither of my dc ever crawled!