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Single Family ResidenceResidential
$863,694$308 / ft²
TopHap EstimateOur estimate of what this home would sell for today, based on nearby sales, the home's size and features, and local price trends. It is a starting point, not an appraisal.· confidence 95How well the pricing models agreed with each other on this home. Higher means the estimate rests on stronger, more consistent data.· as of Aug 30, 2026
Last sold for $169,500 on Jun 15, 1990

21 PORTER ST

BILLERICA, MA 01821
4
Beds
3.5
Baths
2,804 ft²
Living AreaTotal finished area of the structures, from county records. Some counties include shared space like hallways or a building gym, so it may not match a listing.
0.57 ac
Lot SizeThe size of the land the home sits on, from county records.
1977
Year BuiltThe year the home was originally built, according to county records.
2
StoriesHow many floors the home has above ground.
8
RoomsThe total room count in county records. Counties differ on which rooms they count, so compare it loosely.
1
ParkingThe number of parking spaces on the property, including the garage.

Valuation

$864K
$823K low$904K high
Last SaleThe most recent sale price and date from the recorded deed. Transfers between family members or companies may not reflect market value.$169,500 · Jun 15, 1990

Tax & Assessment

Property TaxThe property tax billed for this tax year. It usually pays for schools, roads, and local services.$8,637 (2025)
Assessed ValueThe value the county assigns to this home to calculate property tax. It is often lower than what the home would sell for.$759,600 (2025)
Assessed LandThe share of the county's assessed value that comes from the land itself, not the buildings.$324,300
Assessed ImprovementsThe share of the county's assessed value that comes from the buildings and other structures on the land.$435,300
Assessor Market ValueThe county assessor's own opinion of market value. It is separate from our estimate and updates on the county's schedule.$775,390

Property Facts

Property TypeThe broad category the county puts this property in, such as residential or commercial.Single Family Residence
CountyMIDDLESEX
Lot (acres)The size of the land the home sits on, from county records.0.57
ConstructionThe main material the home's frame and walls are built from.Frame (Unspecified)
RoofThe main material covering the roof, such as asphalt shingle or tile.Asphalt
HeatingThe type of heating system in the home.Electric
CoolingThe type of cooling or air conditioning in the home.Yes
GarageWhether the property has a garage, and details like whether it is attached to the home.Garage, Basement
PoolWhether the property has a pool, and what kind, such as in-ground.No

Transaction History(7)

Sales and refinances filed with the county for this home. Not every transfer is a normal sale, so check the type before comparing prices.

Assigned SchoolsThe public schools this address is zoned for. Boundaries change, so confirm with the district before you count on it.

M
Locke Middle SchoolB+
Middle · Grades 5–7 · 0.4 mi
H
Billerica Memorial High SchoolC
High · Grades 8–12 · 1.1 mi
E
John F KennedyB+
Elementary · Grades KG–4 · 1.3 mi

District: Billerica School District

Neighborhood · ZIP 01821These are comparison scores, not percentages. 100 equals the national average, so 150 means about 50% above average.

CrimeLocal crime compared with the rest of the country, where 100 is average. It reflects things like population density, income, and how crime gets reported.40
Air pollutionOverall air pollution compared with the rest of the country, where 100 is average. Lower is cleaner.100
EarthquakeEarthquake risk and likely building damage compared with the rest of the country, where 100 is average. Scores can run far above 100.82

Index scale: 100 = US average (tick). Lower is better.

Homes occupiedThe share of homes here that someone lives in. The rest sit empty, including vacation and for-sale homes.98%
Bachelor's or higherThe share of adults 25 and older whose highest degree is a bachelor's degree.28%
Poverty rateThe share of people whose household income falls below the federal poverty line, which varies by family size.3.8%
UnemploymentThe share of men 16 and older who are out of work and actively looking. Only men are counted in this figure.1.3%
PopulationHow many people live in this area.31,495
DensityPeople per square mile. Higher numbers mean a more crowded, urban area.1,857 / mi²
Median incomeThe middle household income here — half of households earn more, half earn less.$133,460
Average incomeThe average household income. It runs higher than the median when a few high earners pull it up.$152,991
Average tempThe average temperature here across a full year.49°F
Annual precipHow much rain and melted snow falls here in a typical year.47 in
SunshineThe share of daylight hours that get direct sun in a typical year, counting cloud cover.58%

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Data by ATTOM. Valuations are automated estimates, not appraisals. Photos from Google Street View and may not depict the current property state.

How this home compares

21 Porter St measured against every home in its neighborhood, its ZIP code and its county, using county assessor records refreshed nightly. A home can stand out in one of those areas and look ordinary in another, because each one holds a different mix of homes.

  • Worth more than 86% of homes in Billerica 01821
  • Costs less per square foot than 89% of homes in Middlesex County
  • Bigger than 88% of homes in Billerica 01821
  • Has a bigger lot than 68% of homes in Middlesex County
  • Newer than 70% of homes in Middlesex County

What homes are worth in Billerica 01821

Each bar is how many homes fall in that price range. The marker is this home.

This home
$276K$1.1M

This home is worth more than 86% of homes in Billerica 01821.

How it measures up in Billerica 01821

The dot is this home. The mark in the middle is the typical home in Billerica 01821.

Estimated value$863,694
CheaperTypical $687,795Pricier

Pricier than 86% of homes nearby

Price per ft²$308
CheaperTypical $377Pricier

Pricier than 17% of homes nearby

Living area2,804 ft²
SmallerTypical 1,872 ft²Bigger

Bigger than 88% of homes nearby

Lot size0.57 ac
SmallerTypical 0.57 acBigger

Bigger than 49% of homes nearby

Year built1977
OlderTypical 1970Newer

Newer than 62% of homes nearby

How 21 Porter St ranks against every home in each area.
MeasureThis homeBillerica 01821Middlesex County
Estimated valuepricier than$863,69486% of homes59% of homes
Price per ft²pricier than$30817% of homes11% of homes
Living areabigger than2,804 ft²88% of homes81% of homes
Lot sizebigger than0.57 ac49% of homes68% of homes
Year builtnewer than197762% of homes70% of homes

About 21 Porter St

How much is 21 Porter St, Billerica, MA worth?

The TopHap Estimate for 21 Porter St, Billerica, MA is $863,694 as of Aug 30, 2026. The likely range is $823,468 to $903,920. The estimate is modelled from recorded sales, assessments and the property's own characteristics — it is not an appraisal.

When did 21 Porter St, Billerica, MA last sell?

21 Porter St, Billerica, MA last sold on Jun 15, 1990 for $169,500, according to the county's recorded deed.

How big is 21 Porter St, Billerica, MA?

21 Porter St, Billerica, MA has 4 bedrooms, 3.5 bathrooms, 2,804 square feet of living space and a 0.57-acre lot.

When was 21 Porter St, Billerica, MA built?

21 Porter St, Billerica, MA was built in 1977, making it 49 years old. The building has 2 stories.

What schools serve 21 Porter St, Billerica, MA?

21 Porter St, Billerica, MA is assigned to Locke Middle School (middle), rated B+; Billerica Memorial High School (high), rated C; John F Kennedy (elementary), rated B+. All sit in Billerica School District. Attendance boundaries change — confirm with the district before relying on an assignment.

How does 21 Porter St, Billerica, MA compare to other homes in Billerica 01821?

Among the 10,003 homes in Billerica 01821, it is worth more than 86% of them ($863,694 against a typical $687,795), its price per square foot is higher than 17% of them ($308 against a typical $377), it is bigger than 88% of them (2,804 ft² against a typical 1,872 ft²), its lot is bigger than 49% of them (0.57 ac against a typical 0.57 ac) and it is newer than 62% of them (1977 against a typical 1970). Measured against all of Middlesex County, it is worth more than 59% of homes there. These shares are recounted nightly from the full county assessor record for each area, not from active listings.

What are the property taxes on 21 Porter St, Billerica, MA?

The 2025 property tax bill for 21 Porter St, Billerica, MA was $8,637. The county assessed it at $759,600.

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