Amortization Schedule for a Typical Washington 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 Washington's median home scenario — $524,480 loan at 6.35%:
- Monthly rate r = 6.35% ÷ 12 = 0.5292%
- Monthly payment M = $3,264
- Month 1 interest: $2,775 | Month 1 principal: $489
- After 5 years (60 payments): balance still $490,080
- After 15 years (180 payments): balance still $378,060 (72% of original)
- Total interest over 30 years: $650,560
The key insight: after paying $3,264/month for 15 years — halfway through the loan — you still owe $378,060. This is because early payments are almost entirely interest. Paying just $200 extra per month would save approximately $111,592 in interest and shorten the loan by roughly 4.4 years.