Motocalc is usually very accurate, so I don't understand the difference between their prediction and your measurements. More info would be helpful: name and numbers for motor, name and numbers for ESC, same for the prop and the battery pack.

With decent quality components the numbers you get from the manufacturer usually leave a little "headroom" for heavy-handed modelers - but not always.

Your current draw will drop in the air, but not as much as some claim.

Do you have the throttle pane on Motocalc wide open? Does your TX stick match the setting?
Walt