Use Calculator on iPhone
In the Calculator app 
, you can perform basic arithmetic calculations with the standard calculator. Or use the scientific calculator for exponential, logarithmic, and trigonometric functions.
Ask Siri. Say something like: “What’s 74 times 9?” or “What’s 18 percent of 225?” Learn how to ask Siri.
Use the scientific calculator
Rotate iPhone to landscape orientation.
Copy, delete, or clear numbers
Copy a calculation result: Touch and hold the calculation result in the display, tap Copy, then paste the result somewhere else, such as a note or message.
Delete the last digit: If you make a mistake when you enter a number, swipe left or right on the display at the top.
Clear the display: Tap the Clear (C) key to delete the last entry, or tap the All Clear (AC) key to delete all entries.