Search for a headband calculation formula

Hello, is there a formula to calculate the length of the headband? I have a crossbeam (14*24) that has a distance of 5.55 between the posts (inside edge to inside edge). How can I calculate the length or size of the headband to brace at least this beam in one direction?

A structural engineer can help you. They will consider whether, solid construction, timber framing, prefabricated house, garden house, load on the crossbeam, ceiling load, etc. A collar tie braces a construction, reduces the deflection of the beam, should always be in pairs. So it is important and not a guess.