Most users do not need to download a third-party app. Your iPhone comes with a native Calculator app from Apple that includes a powerful scientific mode.
Tap the calculator icon at the bottom left of the screen and select "Scientific" from the menu. Most users do not need to download a third-party app
Open the Calculator app and rotate your iPhone to landscape mode . Ensure your Portrait Orientation Lock is turned off in the Control Center. Most users do not need to download a third-party app