Which meaning is common for the verb " reckon" "to consider" or "to make a calculation"? Does it sound normal for native speakers?

Perfectly normal for native speakers Mohammad although a little bit "old fashioned". Some examples: "I reckon Brazil will win the world cup" - In my opinion, or I consider that Brazil will win the world cup. "What do you reckon?" - What do you think?

"How much do you reckon that shopping will cost"? - How much do you think or calculate that shopping will cost?

"Wait a minute I will reckon it up" - Wait a minute and I will calculate the cost.

These expressions were certainly used more when I was younger than they are today!