Amortization Schedule for a Typical Massachusetts Home Loan
The amortization formula for a fixed-rate loan is:
M = P × [r(1+r)^n] / [(1+r)^n − 1]
M = monthly payment | P = principal | r = monthly rate (annual ÷ 12) | n = total payments
For Massachusetts's median home scenario — $548,250 loan at 6.35%:
- Monthly rate r = 6.35% ÷ 12 = 0.5292%
- Monthly payment M = $3,411
- Month 1 interest: $2,901 | Month 1 principal: $510
- After 5 years (60 payments): balance still $512,356
- After 15 years (180 payments): balance still $395,472 (72% of original)
- Total interest over 30 years: $679,710
The key insight: after paying $3,411/month for 15 years — halfway through the loan — you still owe $395,472. This is because early payments are almost entirely interest. Paying just $200 extra per month would save approximately $112,161 in interest and shorten the loan by roughly 4.3 years.