Financing · Formula v1.0.0
Mortgage Calculator
Monthly principal & interest plus a full housing-cost estimate: taxes, insurance, HOA and PMI kept clearly separate.
Monthly principal & interest
$1,970.30
Estimated total monthly housing cost $2,445.30
- Loan principalPrice $400,000 − down payment
- $320,000
- Loan-to-value (LTV)
- 80.0%
- Monthly principal & interest
- $1,970.30
- Monthly property tax
- $350.00
- Monthly insurance
- $125.00
- Monthly HOA fee
- $0.00
- Monthly mortgage insurance (PMI)
- $0.00
- Estimated total monthly housing cost
- $2,445.30
- Total interest over the loan
- $389,303
- Total loan payments360 payments of principal + interest
- $709,303
A fixed-rate mortgage payment has two moving parts: principal (repaying the loan) and interest (the lender's charge). Early payments are mostly interest; the share of principal grows every month as the balance falls, this is amortization.
The payment is fixed so that the loan balance reaches exactly zero after the final payment. On top of P&I, homeowners usually pay property tax, insurance, possibly HOA dues and mortgage insurance, this calculator keeps those separate from the loan math.
M = P × r(1+r)ⁿ ÷ ((1+r)ⁿ − 1) where r = annual rate ÷ 12, n = number of monthly payments
P: Loan principal (price minus down payment).
r: Monthly interest rate (annual rate divided by 12).
n: Total number of monthly payments (years × 12).
A $400,000 home with $80,000 down leaves a $320,000 loan. At 6.25% for 30 years, r = 0.0052083 and n = 360.
The fixed principal & interest payment is $1,970.30. Adding $350 tax and $125 insurance gives an estimated $2,445.30 total monthly cost.
Over 30 years, total payments are about $709,306, of which roughly $389,306 is interest. That is why rate and term matter so much.
- •Assumes a fixed nominal annual rate with monthly compounding and end-of-month payments.
- •Does not model adjustable rates, points, origination fees, or rate changes at renewal.
Formula reference
M = P × r(1+r)ⁿ ÷ ((1+r)ⁿ − 1) where r = annual rate ÷ 12, n = number of monthly payments
- P, Loan principal (price minus down payment).
- r, Monthly interest rate (annual rate divided by 12).
- n, Total number of monthly payments (years × 12).