[Definition] The price of the ARM is calculated by adding Index + Margin = Fully Indexed Rate. This is the interest rate your loan would be at without a Start Rate (the introductory special rate for the initial fixed period). This means the loan would be higher if adjusting, typically, 1–3% higher than the fixed rate. Calculating this is important for ARM buyers, since it helps predict the future interest rate of the loan. [Term] 
Fully Indexed Rate
X / Y
F u l l y I n d e x e d R a t e
M a r g i n
I n d e x
S t a r t R a t e
P e r i o d
F l o o r
P a y m e n t S h o c k
C a p