Defaults: Zillow's typical condo value in 02116 (August 2026); Freddie Mac 30-year average (7.28%, week of 10/1/2026). Tax uses Boston's FY2026 residential rate and exemption. An estimate, not a loan offer.
How to use the jumbo loan calculator
- Enter the price of the home you are considering. The calculator starts at $1,299,000, Zillow's typical 02116 condo value for August 2026 rounded to the nearest thousand.
- Set your down payment as a percentage of the price.
- Enter the rate a lender has quoted you, or keep the 7.28% Freddie Mac 30-year average for the week of October 1, 2026.
- Choose a 30- or 15-year term.
- Add the monthly condo fee and the yearly insurance premium if you know them.
- Tick owner-occupied if you will live in the home, so the Boston residential exemption is applied to the tax.
The results show the loan amount, monthly principal and interest, monthly property tax and the total, and a line that tells you whether the loan is above Suffolk County's 2026 conforming limit of $962,550, which makes it a jumbo loan.
What the calculator inputs mean
Home price
The purchase price. The calculator also uses it as a stand-in for the assessed value when it estimates the tax; your actual bill uses Boston Assessing's value, which can differ.
Down payment
The share of the price you pay in cash. The loan is the price minus the down payment. Experian reports jumbo lenders typically want at least 10% down, and some ask for as much as 30%.
Interest rate and term
The annual rate and the length of the loan. Payments use standard monthly amortization: P&I = L x r / (1 - (1 + r)^-n), where r is the annual rate divided by 12 and n is the number of months (360 or 180).
Boston property tax
The tax line uses Boston's FY2026 residential rate of $12.40 per $1,000. With owner-occupied ticked, it first subtracts the FY2026 residential exemption of $351,108 of value, which saves up to $4,353.74 a year. The rates are explained in the guide to Boston property tax and the exemption; FY2027 rates are set in December 2026.
Condo fee
The monthly common charge paid to the condo trust. It varies by building, so ask the trust for the current figure and any planned special assessment. Leave it at zero for a single-family townhouse.
Insurance
Your yearly premium, divided by 12 in the total. NerdWallet's analysis puts the average Boston homeowners policy at about $2,395 a year, but a condo unit policy (HO-6) is priced differently, so use a real quote.
Example on a 02116 condo with 20% down
Using Zillow's exact typical 02116 condo value of $1,298,982 (August 2026), 20% down, 7.28% over 30 years, owner-occupied, with the condo fee and insurance left at zero:
| Line | Amount |
|---|---|
| Down payment (20%) | $259,796.40 |
| Loan amount | $1,039,185.60 |
| Principal and interest | $7,110.24 a month |
| Property tax with exemption | $979.47 a month ($11,753.64 a year) |
| Total before condo fee and insurance | $8,089.71 a month |
| Jumbo check | $76,635.60 above the $962,550 limit |
Without the residential exemption, the tax rises to $1,342.28 a month. With the calculator's default price of $1,299,000, the loan is $1,039,200 and principal and interest come to $7,110.33. For how lenders treat a loan of that size, see jumbo loan rules in Massachusetts.
Monthly payment by loan amount
The table runs the calculator's payment formula on common loan sizes at Freddie Mac's averages for the week of October 1, 2026: 7.28% for a 30-year fixed and 6.60% for a 15-year fixed. It shows principal and interest only, and total interest assumes the loan is held to term with no extra payments.
| Loan amount | 30-year at 7.28% | Total interest, 30 years | 15-year at 6.60% | Total interest, 15 years |
|---|---|---|---|---|
| $300,000 | $2,052.64 | $438,949.26 | $2,629.84 | $173,371.64 |
| $400,000 | $2,736.85 | $585,265.69 | $3,506.46 | $231,162.18 |
| $962,550 (Suffolk County limit) | $6,585.89 | $1,408,368.72 | $8,437.85 | $556,262.90 |
| $1,000,000 | $6,842.12 | $1,463,164.22 | $8,766.14 | $577,905.45 |
| $1,039,185.60 (02116 condo, 20% down) | $7,110.24 | $1,520,499.18 | $9,109.65 | $600,551.03 |
| $1,455,186.40 (02116 single-family, 20% down) | $9,956.56 | $2,129,176.67 | $12,756.37 | $840,960.16 |
| $2,000,000 | $13,684.25 | $2,926,328.43 | $17,532.28 | $1,155,810.91 |
Every row above $962,550 is a jumbo loan in Suffolk County. The two 02116 rows use Zillow's typical condo and single-family values for August 2026.
How the rate and term change the payment
Interest rate
On the 02116 condo loan of $1,039,185.60 over 30 years, each half point moves the payment by about $350 a month. The 6.78% and 7.78% rows are illustrations half a point either side of the Freddie Mac average, not quotes.
| Rate | Monthly principal and interest | Total interest, 30 years |
|---|---|---|
| 6.78% | $6,760.87 | $1,394,729.09 |
| 7.28% (Freddie Mac average) | $7,110.24 | $1,520,499.18 |
| 7.78% | $7,466.41 | $1,648,721.22 |
15-year or 30-year term
On the same loan, the 15-year option at the 6.60% average costs $9,109.65 a month, $1,999.41 more than the 30-year payment, but total interest falls from $1,520,499.18 to $600,551.03, a difference of $919,948.15. A lender counts the higher payment in your debt-to-income ratio, so a shorter term can make a jumbo approval harder. Switch the term in the calculator to compare your own figures.
What the calculator leaves out
- Mortgage insurance. If you put less than 20% down, a lender may charge mortgage insurance; ask for the amount.
- Special assessments. A condo trust can levy one-off charges for roofs, facades or other building work on top of the monthly fee.
- The CPA surcharge. Boston's 1% Community Preservation Act surcharge adds $105.14 a year on the example condo with the exemption.
- Closing costs. Recording fees, title insurance and attorney fees are paid once at purchase; the breakdown of Massachusetts closing costs lists them.
- Utilities, parking and upkeep. These depend on the home.
If you already own in Back Bay and want to know what your current home could fund, a pricing review of your Back Bay home is the starting point.
Frequently asked questions
Do you have to put 20% down for a jumbo loan?
Not always. Experian reports jumbo lenders typically want at least 10% down, and some require as much as 30%. On a $1,298,982 Back Bay condo, 10% down is $129,898.20 and 20% is $259,796.40. Each lender sets its own minimum and may charge mortgage insurance below 20%, so ask for written terms and enter your own down payment in the calculator.
Is $400,000 considered a jumbo loan?
No. In Suffolk County, which includes Boston, a one-unit loan is a jumbo loan only above FHFA's 2026 conforming limit of $962,550. A $400,000 loan is conforming everywhere in Massachusetts, where no county limit is below the $832,750 national baseline. The calculator flags any loan above $962,550.
What is the monthly payment on a $1,000,000 loan?
At Freddie Mac's 30-year fixed average of 7.28% for the week of October 1, 2026, principal and interest on $1,000,000 are $6,842.12 a month. Over 15 years at the 6.60% average they are $8,766.14. In Suffolk County a $1,000,000 loan is a jumbo loan, and property tax, insurance and any condo fee come on top.
How much interest do you pay on a $300,000 house over 30 years?
It depends on the loan, not the price. A $300,000 loan at 7.28% over 30 years pays $438,949.26 in interest if held to term, with principal and interest of $2,052.64 a month. With 20% down on a $300,000 house the loan is $240,000, and the interest comes to $351,159.41. Extra payments or a shorter term reduce it.
What is a 30-year jumbo loan rate today?
Jumbo rates are quoted by each lender, so there is no single published jumbo rate. As a benchmark, Freddie Mac's Primary Mortgage Market Survey put the 30-year fixed average at 7.28% for the week of October 1, 2026, and the 15-year average at 6.60%. The calculator defaults to 7.28%; replace it with the rate a lender quotes you.
What is the downside of a jumbo loan?
Jumbo loans usually come with tighter requirements. Experian reports lenders often want a credit score of 700 to 720 or higher, a debt-to-income ratio no higher than 43%, cash reserves of up to 12 months of payments, and sometimes two appraisals. Condo buyers also need the building to pass the lender's own review. The loan itself is larger, so total interest is larger too.
Is it hard to qualify for a jumbo loan?
It is stricter than a conforming loan because Fannie Mae and Freddie Mac do not buy jumbo loans, so each lender sets its own standards. Experian reports common ranges: a credit score of at least 700, 10% to 30% down, a debt-to-income ratio of 43% or lower and up to 12 months of reserves. No calculator can predict approval; ask lenders directly.
Does the calculator include the Boston residential exemption?
Yes. With owner-occupied ticked, it subtracts the FY2026 residential exemption of $351,108 from the price before applying the $12.40 per $1,000 rate. On a $1,298,982 condo that gives $979.47 a month instead of $1,342.28. It uses the price as the assessed value, which is only an approximation, and it leaves out the CPA surcharge.
Sources
- Freddie Mac: Primary Mortgage Market Survey, week of October 1, 2026
- FHFA: Conforming loan limits for 2026, full county list
- FHFA: FHFA announces conforming loan limit values for 2026
- Experian: What is a jumbo loan?
- City of Boston Assessing: How we tax your property
- City of Boston Assessing: Residential exemption
- City of Boston Assessing: Community Preservation Act
- NerdWallet: The best home insurance in Massachusetts in 2026
- Zillow Research: Home Value Index (ZHVI) data, August 2026