The word "reckon" isn't heard very often in the US. Most people would consider it quaint or dialectical. I don't think you'd ever hear a TV reporter say it. I think it's used mainly in the South. My father used it a lot. He grew up on a farm in Kentucky.

I was surprised and pleased to find it is rather common in the UK.

"How much do you reckon it'll cost?"

"I reckon we'll have some rain this afternoon."

"I reckon it's about time to eat."