the answer to your question is not that simple. Without knowing more detail of the connection, an answer is not possible. What is the loading of the joint ? Is it tension or shear or both ? Is it fatigue critical ? You find simple equations in text books but the detail analysis of preload in bolted connection is more complex. Many papers have been written all over the world on the subject."How much preload is enough ?" is one of the many questions. Because that will finally effect the run-on torque. The two simple euqations for a preliminary estimate found are:
For dry bolts Torque = ( Ppreload * 2 rb ) / 5
For lubed bolts Torque = ( Ppreload * 2 rb ) / 6.7
2rb is the shank diameter of the bolt !