A monthly mortgage payment has four parts, called PITI: principal, interest, taxes, and insurance (plus HOA and any Mello-Roos). This calculator handles principal, interest, and the property-tax impound, and explains the amortization math. On the approximate Northridge median of $1,205,000, the figures below are computed at illustrative terms - your real numbers come from your lender. Estimates only.
What this calculator does
It uses the standard amortization formula to return monthly principal & interest, adds the property-tax impound, and includes HOA. It does not include PMI (on less than 20% down), homeowners insurance (highly variable in California, especially in fire-exposed areas), FHA/VA fees, or ARM resets. Treat the output as a planning figure; your lender's Loan Estimate is binding.
The math
The monthly principal & interest on a fixed-rate loan is M = P × [ r(1+r)n ] / [ (1+r)n − 1 ], where P is the loan amount, r is the monthly rate (annual / 12), and n is the number of payments (360 for a 30-year). The property-tax impound is the annual tax divided by 12.
Worked example for Northridge
On the Northridge median of $1,205,000, 20% down is a $964,000 loan. At 6.75% over 30 years, principal & interest is about $6,252/mo. At a 1.15% property-tax rate, the impound is about $1,155/mo, for roughly $7,407/mo before homeowners insurance, HOA, and any Mello-Roos.
Try the calculator
Enter your own numbers. Confirm everything with your lender before deciding.
Estimate only. Homeowners insurance, PMI, and exact lender fees are not included. Confirm with your lender.
What buyers forget
- Homeowners insurance - not in this tool; California premiums vary widely, and far more in CAL FIRE Very High Fire Hazard Severity Zones.
- Mello-Roos - add it to the tax line for newer tracts.
- PMI - applies under 20% down (roughly 0.3-1.5% of loan annually until 20% equity).
- Prop 13 escalator - assessed value can rise up to ~2%/yr, so your impound grows over time.
Frequently Asked Questions
How is the monthly mortgage payment calculated?
Using the amortization formula M = P×[r(1+r)^n]/[(1+r)^n-1], where P is the loan, r is the monthly rate (annual/12), and n is the number of payments (360 for 30 years). Then add monthly property tax, insurance, and HOA.
What property tax rate should I use for Northridge?
About 1.15% is a reasonable default (1.0% Prop 13 base plus local voter-approved bonds), but verify the parcel, and add Mello-Roos if the tract has a CFD. Confirm with the county assessor.
Does this include PMI or homeowners insurance?
No. PMI applies to conventional loans under 20% down (roughly 0.3-1.5% of the loan annually until 20% equity), and homeowners insurance is not included because California premiums vary widely. Add both to your budget.
Should I choose a 30-year or 15-year loan?
A 30-year has a lower monthly payment and more flexibility; a 15-year carries a higher payment but far less lifetime interest. The right choice depends on your cash flow, other goals, and how long you'll own. Brian is a REALTOR, not a lender - confirm with a loan officer.
How much do I need to earn to buy at the Northridge median?
Lenders typically allow a 43-50% back-end debt-to-income ratio, so the income needed depends on the full PITI plus your other debts and current rates. Get a real pre-approval from a licensed lender for your situation.
