Tempered glass frequently is used in home windows. It is glass that has been heated to a softening point and cooled, which strengthens the glass. When tempered glass shatters, it forms small pieces with rounded edges, instead of sharp, jagged chunks. The strength of any piece of glass depends on its structure. Also, the glass can't be realigned exactly, and filling a crack is never perfect. If a piece of tempered glass is cracked, the whole piece is compromised, and to get it looking and working like new, the entire piece needs to be replaced.
Break out the existing, broken pane of glass using a crowbar. Don't damage other panes of glass in the process. Wear work gloves when touching the shards of glass stuck in the frame of the window.
Measure the height and width of the opening with the tape measure. Be precise because little room exists for error. Mark the desired size on the new pane of tempered glass with pieces of tape. Using the ruler, cut straight lines along the marks using the glass cutter. The glass cutter will make a shallow cut along the edge of the glass. Carefully break the pane of glass along that cut line.
Apply a line of adhesive sealant along the edge of the frame. Place the new pane of glass into the frame. Allow the sealant ample time to harden, at least 30 minutes. Apply a line of clear caulk around the edge of the glass to create a weather seal.