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Single Family ResidenceResidential
$1,068,568$1,243 / 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 94How well the pricing models agreed with each other on this home. Higher means the estimate rests on stronger, more consistent data.· as of Sep 24, 2026

3921 ONEILL DR

SAN MATEO, CA 94403
2
Beds
1
Baths
860 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.
0.11 ac
Lot SizeThe size of the land the home sits on, from county records.
1950
Year BuiltThe year the home was originally built, according to county records.
1
StoriesHow many floors the home has above ground.
4
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

$1.1M
$1M low$1.1M high

Tax & Assessment

Property TaxThe property tax billed for this tax year. It usually pays for schools, roads, and local services.$2,838 (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.$89,594 (2026)
Assessed LandThe share of the county's assessed value that comes from the land itself, not the buildings.$29,949
Assessed ImprovementsThe share of the county's assessed value that comes from the buildings and other structures on the land.$59,645
Previous AssessedThe county's assessed value from the year before, useful for seeing how the assessment changed.$87,838
Assessor Market ValueThe county assessor's own opinion of market value. It is separate from our estimate and updates on the county's schedule.$1,237,770

Climate Risk

Projected Flood DepthHow deep a serious flood is expected to get here at some point in the next 30 years. Shown in inches.26 in
30-Year Flood ChanceThe chance of at least one serious flood here in the next 30 years, not in any single year.30%
FEMA Flood ZoneFEMA's flood zone for this address. Zones starting with A or V are high risk, and lenders usually require flood insurance there.1 percent flood zone

Scores 0–100; higher = greater projected risk.

Property Facts

Property TypeThe broad category the county puts this property in, such as residential or commercial.Single Family Residence
CountySAN MATEO
Lot (acres)The size of the land the home sits on, from county records.0.12
HeatingThe type of heating system in the home.Central
CoolingThe type of cooling or air conditioning in the home.Central
PoolWhether the property has a pool, and what kind, such as in-ground.No

Transaction History(5)

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.

E
George Hall Elementary SchoolA
Elementary · Grades KG–5 · 0.3 mi
M
Abbott Middle SchoolC
Middle · Grades 6–8 · 1.4 mi
H
Hillsdale High SchoolA
High · Grades 9–12 · 1.5 mi

District: San Mateo-Foster City Elementary School District

Neighborhood · ZIP 94403These 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.104
Air pollutionOverall air pollution compared with the rest of the country, where 100 is average. Lower is cleaner.85
EarthquakeEarthquake risk and likely building damage compared with the rest of the country, where 100 is average. Scores can run far above 100.516

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.96%
Bachelor's or higherThe share of adults 25 and older whose highest degree is a bachelor's degree.34%
Poverty rateThe share of people whose household income falls below the federal poverty line, which varies by family size.7.9%
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.43,216
DensityPeople per square mile. Higher numbers mean a more crowded, urban area.7,529 / mi²
Median incomeThe middle household income here — half of households earn more, half earn less.$160,514
Average incomeThe average household income. It runs higher than the median when a few high earners pull it up.$196,016
Average tempThe average temperature here across a full year.58°F
Annual precipHow much rain and melted snow falls here in a typical year.21 in
SunshineThe share of daylight hours that get direct sun in a typical year, counting cloud cover.66%

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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

3921 Oneill Dr 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 less than 86% of homes in San Mateo 94403
  • Costs more per square foot than 75% of homes in San Mateo Village
  • Smaller than 95% of homes in San Mateo 94403
  • Has a smaller lot than 95% of homes in San Mateo Village
  • Older than 71% of homes in San Mateo County

What homes are worth in San Mateo 94403

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

This home
$558K$2.9M

This home is worth more than 14% of homes in San Mateo 94403.

How it measures up in San Mateo 94403

The dot is this home. The mark in the middle is the typical home in San Mateo 94403.

Estimated value$1,068,568
CheaperTypical $1,725,136Pricier

Pricier than 14% of homes nearby

Price per ft²$1243
CheaperTypical $1073Pricier

Pricier than 75% of homes nearby

Living area860 ft²
SmallerTypical 1,540 ft²Bigger

Bigger than 5% of homes nearby

Lot size0.11 ac
SmallerTypical 0.14 acBigger

Bigger than 6% of homes nearby

Year built1950
OlderTypical 1955Newer

Newer than 31% of homes nearby

How 3921 Oneill Dr ranks against every home in each area.
MeasureThis homeSan Mateo VillageSan Mateo 94403San Mateo County
Estimated valuepricier than$1,068,56826% of homes14% of homes25% of homes
Price per ft²pricier than$124375% of homes75% of homes74% of homes
Living areabigger than860 ft²12% of homes5% of homes6% of homes
Lot sizebigger than0.11 ac5% of homes6% of homes24% of homes
Year builtnewer than195034% of homes31% of homes29% of homes

About 3921 Oneill Dr

How much is 3921 Oneill Dr, San Mateo, CA worth?

The TopHap Estimate for 3921 Oneill Dr, San Mateo, CA is $1,068,568 as of Sep 24, 2026. The likely range is $1,004,712 to $1,132,424. The estimate is modelled from recorded sales, assessments and the property's own characteristics — it is not an appraisal.

When did 3921 Oneill Dr, San Mateo, CA last sell?

3921 Oneill Dr, San Mateo, CA last sold on Jan 1, 1900, according to the county's recorded deed.

How big is 3921 Oneill Dr, San Mateo, CA?

3921 Oneill Dr, San Mateo, CA has 2 bedrooms, 1 bathrooms, 860 square feet of living space and a 0.12-acre lot.

When was 3921 Oneill Dr, San Mateo, CA built?

3921 Oneill Dr, San Mateo, CA was built in 1950, making it 76 years old. The building has 1 story.

What schools serve 3921 Oneill Dr, San Mateo, CA?

3921 Oneill Dr, San Mateo, CA is assigned to George Hall Elementary School (elementary), rated A; Abbott Middle School (middle), rated C; Hillsdale High School (high), rated A. All sit in San Mateo-Foster City Elementary School District. Attendance boundaries change — confirm with the district before relying on an assignment.

How does 3921 Oneill Dr, San Mateo, CA compare to other homes in San Mateo 94403?

Among the 11,697 homes in San Mateo 94403, it is worth more than 14% of them ($1,068,568 against a typical $1,725,136), its price per square foot is higher than 75% of them ($1243 against a typical $1073), it is bigger than 5% of them (860 ft² against a typical 1,540 ft²), its lot is bigger than 6% of them (0.11 ac against a typical 0.14 ac) and it is newer than 31% of them (1950 against a typical 1955). Measured against all of San Mateo County, it is worth more than 25% 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 3921 Oneill Dr, San Mateo, CA?

The 2025 property tax bill for 3921 Oneill Dr, San Mateo, CA was $2,838. The county assessed it at $89,594.

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