Lenders quote you a monthly payment that quietly excludes taxes, insurance, and PMI. Here is the math they skip — PITI, extra payments, the rent-vs-buy crossover — with calculators that run entirely in your browser.
1. Your Real Payment Is PITI, Not P&I
The number a bank advertises is principal and interest only. Your actual monthly cost adds property tax, homeowner’s insurance, HOA dues, and — if your down payment is under 20% — PMI. On a $400,000 home with 10% down, PMI alone adds roughly $150/month that the headline rate never mentioned.
A full PITI calculator shows every component as its own line, and adds PMI automatically only when your down payment is below 20% — at 20%+ it zeroes out, exactly like real lenders treat it.
Mortgage Calculator with PMI & TaxesFull PITI breakdown, auto-PMI under 20% down, extra-payment payoff comparison with a savings curve.→2. Extra Payments: the Five-Figure Lever
Adding $100–$500 to your monthly payment goes straight to principal, and the effect is non-linear: on a 30-year loan at 6.8%, $200 extra per month typically cuts 6–8 years off the term and saves five figures of interest. You cannot feel that from a single number — you need to see the two balance curves diverge.
The mortgage calculator above plots exactly that: your balance with and without the extra payment, with the gap between the curves shaded. The shaded area is the interest you never pay.
3. Rent vs Buy: Find Your Crossover Year
“Renting is throwing money away” is true starting in year N — the question is what N is. Buying front-loads the down payment and closing friction; renting keeps rising every year. In expensive markets the cumulative cost curves often cross around year 5–8; in cheap ones, year 2.
Rent vs Buy CalculatorCumulative rent vs net buy cost plotted year by year — the crossover point is the answer.→4. Any Loan, With the Full Amortization Schedule
Car loans and personal loans use the same amortization math as mortgages. What most calculators hide is the schedule itself: the month-by-month split of principal vs interest — where you discover your first year of payments is mostly interest.
Loan Calculator with Amortization ScheduleMonthly payment, total interest, and the full payment-by-payment schedule with a balance curve.→Auto Loan CalculatorVehicle price, down payment, trade-in, and sales tax — the true cost of driving off the lot.→5. The Minimum-Payment Trap
Credit card minimums are engineered to stretch payoff to decades: on a $5,000 balance at 20% APR, paying only the minimum can take over 15 years and double the real cost. Paying $50 more per month collapses that timeline.
Credit Card Minimum Payment CalculatorSee how little of your minimum goes to principal, and the payoff curve for minimums vs +$50/month.→Credit Card Payoff CalculatorSet a fixed monthly payment and get the exact payoff date, total interest, and balance curve.→6. Compounding, Working for You Instead
The same math that stretches a card balance to 15 years also grows a retirement fund — if you give it time. The compound interest calculator shows your contributions vs the growth on top, plus a dashed line for “the same money, started 10 years later.” The gap between those two lines is the most expensive procrastination most people ever commit.
Compound Interest CalculatorContributions vs compound growth, with a start-now vs wait-10-years comparison.→Retirement CalculatorProject your nest egg from age, savings, and monthly contributions — plus the 4% rule income.→Why These Calculators Feel Fast
Every calculator linked above is a static page that runs 100% in your browser. Your salary, balance, and birth date never leave the device — there is no server to send them to. That is also why results update instantly while you drag a slider: no round-trip, no spinners, no “submitting…”.