Four calculators, four different questions. Don’t make one of them answer the others.
The money tools on this site each answer one question. Mixing them up is how a mortgage payment gets treated as a budget, or a debt slogan gets treated as a plan. Here is a set of inputs you can type yourself, and what the result is for.
The mortgage calculator uses the standard fixed payment. A $400,000 house with $80,000 down is a $320,000 loan. At 6.5% for 30 years the principal and interest is $2,022.62, and the interest over the full term is about $408,000. The same loan at 6.25% for 15 years is $2,744 a month and about $174,000 of interest. You pay about $720 more each month and avoid about $234,000 of interest. Tax and insurance sit on top and do not shrink the loan. On this house, $4,800 of tax and $1,200 of insurance add $500 a month, so the 30-year housing payment is about $2,523 before HOA dues or mortgage insurance.
Enter the rate, not the APR. The CFPB explains the difference. Private mortgage insurance, which the CFPB also explains, is missing if you put less than 20% down. Add the lender’s quote yourself.
The affordability calculator goes the other direction. Someone earning $90,000, with $400 of other monthly debt, $40,000 down, a 6.5% rate, 30 years, tax at 1.1% of price, and $1,500 of insurance, has a 28% front-end cap of about $2,100 a month. The 36% back-end cap minus the $400 is about $2,300, so the front cap binds. The price that falls out is roughly $308,000. The looser rows on the page will print a higher price from the same paycheck. They are not a preapproval. The CFPB’s debt-to-income explanation is why the other-debt box matters: leave out a car payment and the house gets bigger than a lender will allow.
Renting versus buying is a third question. The rent-versus-buy page is sensitive to how long you stay, because closing costs and selling costs are front-loaded. If you would not invest the down payment, set that return near zero or the rent side is being given credit you will not earn.
The debt planner is a simulator. Two debts: $1,200 at 8% with a $40 minimum, and $4,500 at 24% with a $120 minimum, plus $150 extra each month. Snowball and avalanche both finish in about 23 months. Avalanche, which attacks the 24% balance first, costs roughly $230 less interest. Minimums only, with no extra, take about 58 months and something over $3,500 of interest. The extra payment is the decision. The label is the fine print.
A single student loan is simpler. On the student-loan page, $30,000 at 6.5% with a $350 payment takes about 9.6 years and about $10,400 of interest. Federal income-driven plans are not this formula. Those live on StudentAid.gov.
The retirement calculator grows a balance and then deflates it. Age 35, retire at 65, $20,000 saved, $500 a month, 7% return, 3% inflation: about $772,000 nominal, about $318,000 in today’s dollars. Four percent of the nominal pile is about $2,570 a month. Four percent of the inflation-adjusted pile is about $1,060 in today’s buying power. Read the second figure if the question is what the money buys. The path assumes every year returns 7%. Investor.gov’s compound-interest note is the idea, not a forecast. Social Security is not in the number.
Net worth, on the net-worth page, is what you could sell minus what you owe. A $350,000 house with a $240,000 mortgage is $110,000, not $350,000.
Last updated: October 29, 2026. Estimates only. Not tax, legal, financial, or professional advice. See the terms.