Rate Sensitivity Engine
A mortgage rate move of half a point changes what you pay every month for up to three decades. Enter your numbers to see the monthly payment, lifetime interest and total cost at each rate from 5.0% to 8.0% — so you can see exactly how sensitive your budget is before you lock.
| Rate | P&I / mo | Total / mo | Lifetime interest | Total cost |
|---|---|---|---|---|
| 5.00% | $2,147 | $2,756 | $373,023 | $388,023 |
| 5.50% | $2,271 | $2,879 | $417,616 | $432,616 |
| 6.00% | $2,398 | $3,007 | $463,353 | $478,353 |
| 6.50% | $2,528 | $3,137 | $510,178 | $525,178 |
| 7.00% | $2,661 | $3,270 | $558,036 | $573,036 |
| 7.50% | $2,797 | $3,405 | $606,869 | $621,869 |
| 8.00% | $2,935 | $3,543 | $656,621 | $671,621 |
Rate assumption: you are comparing a rate ladder from 5.00% to 8.00% on a fixed-rate 30-year loan. Your actual rate depends on credit score, LTV, loan type, lender and points.
Data source: the current benchmark 30-year fixed average (6.71%) is the Freddie Mac Primary Mortgage Market Survey (PMMS) national average as of 2026-09-03; the ladder brackets it.
Calculation date: 2026-09-21. Formula: standard fixed-rate amortization, verified against golden vectors.
What the columns mean
- • P&I / mo = principal and interest on the loan amount at that rate.
- • Total / mo = P&I + property tax + insurance + mortgage insurance (if applicable).
- • Lifetime interest = all scheduled interest over the full term.
- • Total cost = lifetime interest + an estimated 3% of price for closing costs.
Go deeper
- Scenario Engine — compare down-payment scenarios
- Mortgage calculator (PITI) — full payment breakdown
- Refinance calculator — when a lower rate pays off
- Mortgage rate lock guide — timing a lock
- Today’s mortgage rates — benchmark by state
Methodology & Assumptions
How this calculator works, what it assumes, and where it falls short. Every calculator on TruePITI documents its math.
Formula
- P&I = L · r(1+r)^n / [(1+r)^n − 1], where L = loan amount, r = annual rate / 12, n = term months. The same formula is evaluated at each rate from 5.0% to 8.0%; total monthly cost adds tax, insurance and mortgage insurance.
Assumptions
- Fixed-rate fully-amortized loan over the selected term. Rates are annual nominal.
- The default benchmark (6.71%) is the Freddie Mac PMMS national 30-year average as of 2026-09-03; the 5.0%–8.0% ladder brackets it.
- Property tax and insurance are held constant across all rates and do not amortize.
- This shows the cost of a given rate; it does not forecast where rates will go.
Limitations
- Does not model rate buydowns/points, ARM resets, or lender-specific pricing adjustments.
- Assumes one rate holds for the full term (no refinance or reset).
- Total cost includes an estimated 3% closing cost, not a quoted figure.
Sources
- Freddie Mac Primary Mortgage Market Survey (PMMS)
- CFPB — mortgage interest and amortization basics
Last updated: 2026-09-21. Estimates only — verify rates with your lender before locking.