BoltCalcPhone is a simple to use tool that calculates the required bolt size iteratively with a rough calculation.
It is not a complete proof of strength according to VDI 2230 Part 1, but a simplified calculation with few input parameters. Therefore, reasonable assumptions are made for the missing parameters.
For torque controlled tightening the mounting torque is calculated. For angle controlled tightening the mounting torque is calculated and determined simplifies the further rotation angle.