Mortgage Calculator: Principal, Interest and Ownership Budget
Estimate fixed-rate principal and interest separately from taxes, insurance, mortgage insurance and HOA assumptions. Costs entered here are hypothetical;the result is not a lender offer, disclosed APR or eligibility decision.
Published October 23, 2026 · Borrow Your Loan
Which payment does this calculator estimate?
It first calculates fixed monthly principal and interest using loan principal, the nominal note interest rate and the term. It then adds the explicit nonloan-cost inputs to show an estimated ownership budget. This is not an actual lender payment, escrow analysis, APR calculation, qualification decision or complete household budget.
Annual tax and insurance inputs are divided by 12. Mortgage insurance and HOA are monthly inputs;enter0 where the assumption does not apply. Do not also add an escrow total covering the same expenses. Closing costs, maintenance, utilities and future changes are excluded.
Change the hypothetical inputs
Monthly principal and interest: $1,798.65
Monthly ownership-budget estimate: $2,848.65
Full-term interest on this loan: $347,514.57
360 fixed monthly payments;nonloan costs are added separately.
How does the default example break down?
| Component | Monthly amount | Scope |
|---|---|---|
| Principal and interest | $1,798.65 | Fixed 300K/6%/360-month mathematical example. |
| Property tax budget | $500.00 | Invented annual tax assumption of $6,000 divided by 12. |
| Homeowners insurance budget | $200.00 | Invented annual premium of $2,400 divided by 12. |
| Mortgage insurance assumption | $150.00 | Optional input for illustration; not a determination that it applies. |
| HOA assumption | $200.00 | May be paid separately; not assumed to be escrow. |
| Estimated monthly ownership budget | $2,848.65 | Sum of the above, not a lender payment or full household budget. |
If only the tax assumption rises 20% and the homeowners-insurance assumption rises 25%, this illustrated budget increases by $150 per month. That is sensitivity arithmetic, not a tax or premium forecast. Do not add escrow again when its tax/insurance components are already included. Maintenance, utilities and other household expenses are not modeled.
What changes with the term?
| Term | Monthly P&I only | Full-term interest | Interest in first 60 payments | Principal after 60 payments |
|---|---|---|---|---|
| 15 years | $2,531.57 | $155,682.69 | $79,921.52 | $228,027.30 |
| 30 years | $1,798.65 | $347,514.57 | $87,082.16 | $279,163.07 |
The 15-year case requires more monthly cash and repays principal faster. The 30-year case has a smaller scheduled P&I payment but a longer payoff period. Taxes, insurance, mortgage insurance, HOA and closing costs are excluded from this table. Full-precision payments are used before rounding.
How can you verify the mathematics?
The calculator uses P × r / (1 − (1+r)−n), with monthly rate r = annual note-rate percentage /1200 and number of payments n = years ×12. At 0%, payment is principal/n. Full-term interest equals the unrounded P&I payment multiplied by n, minus starting principal. The ownership-budget result adds annual tax/12, annual insurance/12, monthly mortgage insurance and monthly HOA.
Read the original 60-case methodology and reproduction code. Actual lenders’ terms, accrual and rounding may differ. The CFPB PITI explanation distinguishes core payment components. Use the master mortgage guide, affordability resource and DTI resource for separate decision questions.
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