In our formulaes BDY= D/F * 360/t EAY= (1+HPR)^365/t RMM= HPR*360/t Forward premium= (Forward/Spot - 1)*360/t we use 360/t, but for the following PV=FV(1+r)^t/365 Interest rate swap payments = (fixed - libor)*t/360*notional FRA net payments = (floating - forward)*t/360 / (1+floating)*t/360 option discounting = S-X/(1+r)^t/365 we use t/360 Can someone please explain when you use t/360 vs 360/t? Thanks

u use 360/t when the yield ur applying is the yield of the period. This will turn it into annual form. When given an annual yield, u apply t/360 to turn it into the equivalent period form.

just ask yourself what exactly it is you’re trying to work out… are you trying to annualise your answer? or do you want the yield for a specific period?