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Single Family ResidenceResidential
$828,020$749 / 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

20321 SAPPHIRE ST

CASTRO VALLEY, CA 94546
3
Beds
1
Baths
1,106 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.
0.12 ac
Lot SizeThe size of the land the home sits on, from county records.
1952
Year BuiltThe year the home was originally built, according to county records.
1
StoriesHow many floors the home has above ground.
5
RoomsThe total room count in county records. Counties differ on which rooms they count, so compare it loosely.

Valuation

$828K
$781K low$875K high

Tax & Assessment

Property TaxThe property tax billed for this tax year. It usually pays for schools, roads, and local services.$3,038 (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.$187,486 (2026)
Assessed LandThe share of the county's assessed value that comes from the land itself, not the buildings.$87,625
Assessed ImprovementsThe share of the county's assessed value that comes from the buildings and other structures on the land.$99,861
Previous AssessedThe county's assessed value from the year before, useful for seeing how the assessment changed.$183,810
Assessor Market ValueThe county assessor's own opinion of market value. It is separate from our estimate and updates on the county's schedule.$888,660

Property Facts

Property TypeThe broad category the county puts this property in, such as residential or commercial.Single Family Residence
CountyALAMEDA
Effective Year BuiltAn adjusted build year that accounts for condition and major remodels. A big renovation can make a home count as newer than it is.1953
Lot (acres)The size of the land the home sits on, from county records.0.12
ConstructionThe main material the home's frame and walls are built from.Wood (Unspecified)
RoofThe main material covering the roof, such as asphalt shingle or tile.Composition Shingle
PoolWhether the property has a pool, and what kind, such as in-ground.No

Transaction History(3)

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
Creekside Middle SchoolA
Middle · Grades 6–8 · 0.2 mi
E
Marshall Elementary SchoolA
Elementary · Grades KG–5 · 0.4 mi
H
Castro Valley High SchoolA-
High · Grades 9–12 · 1.1 mi

District: Castro Valley Unified School District

Neighborhood · ZIP 94546These 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.78
Air pollutionOverall air pollution compared with the rest of the country, where 100 is average. Lower is cleaner.91
EarthquakeEarthquake risk and likely building damage compared with the rest of the country, where 100 is average. Scores can run far above 100.657

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.27%
Poverty rateThe share of people whose household income falls below the federal poverty line, which varies by family size.8.9%
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.46,776
DensityPeople per square mile. Higher numbers mean a more crowded, urban area.4,466 / mi²
Median incomeThe middle household income here — half of households earn more, half earn less.$117,352
Average incomeThe average household income. It runs higher than the median when a few high earners pull it up.$142,642
Average tempThe average temperature here across a full year.57°F
Annual precipHow much rain and melted snow falls here in a typical year.23 in
SunshineThe share of daylight hours that get direct sun in a typical year, counting cloud cover.78%

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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

20321 Sapphire 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 less than 78% of homes in Castro Valley
  • Costs more per square foot than 87% of homes in Castro Valley
  • Smaller than 88% of homes in Castro Valley
  • Has a smaller lot than 82% of homes in Castro Valley 94546
  • Older than 70% of homes in Castro Valley

What homes are worth in Castro Valley 94546

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

This home
$450K$1.8M

This home is worth more than 28% of homes in Castro Valley 94546.

How it measures up in Castro Valley 94546

The dot is this home. The mark in the middle is the typical home in Castro Valley 94546.

Estimated value$828,020
CheaperTypical $989,959Pricier

Pricier than 28% of homes nearby

Price per ft²$749
CheaperTypical $627Pricier

Pricier than 85% of homes nearby

Living area1,106 ft²
SmallerTypical 1,540 ft²Bigger

Bigger than 17% of homes nearby

Lot size0.12 ac
SmallerTypical 0.15 acBigger

Bigger than 18% of homes nearby

Year built1952
OlderTypical 1956Newer

Newer than 38% of homes nearby

How 20321 Sapphire St ranks against every home in each area.
MeasureThis homeCastro ValleyCastro Valley 94546Alameda County
Estimated valuepricier than$828,02022% of homes28% of homes34% of homes
Price per ft²pricier than$74987% of homes85% of homes66% of homes
Living areabigger than1,106 ft²12% of homes17% of homes19% of homes
Lot sizebigger than0.12 ac23% of homes18% of homes36% of homes
Year builtnewer than195230% of homes38% of homes35% of homes

About 20321 Sapphire St

How much is 20321 Sapphire St, Castro Valley, CA worth?

The TopHap Estimate for 20321 Sapphire St, Castro Valley, CA is $828,020 as of Sep 24, 2026. The likely range is $780,862 to $875,178. The estimate is modelled from recorded sales, assessments and the property's own characteristics — it is not an appraisal.

When did 20321 Sapphire St, Castro Valley, CA last sell?

20321 Sapphire St, Castro Valley, CA last sold on Jan 1, 1900, according to the county's recorded deed.

How big is 20321 Sapphire St, Castro Valley, CA?

20321 Sapphire St, Castro Valley, CA has 3 bedrooms, 1 bathrooms, 1,106 square feet of living space and a 0.12-acre lot.

When was 20321 Sapphire St, Castro Valley, CA built?

20321 Sapphire St, Castro Valley, CA was built in 1952, making it 74 years old. The building has 1 story.

What schools serve 20321 Sapphire St, Castro Valley, CA?

20321 Sapphire St, Castro Valley, CA is assigned to Creekside Middle School (middle), rated A; Marshall Elementary School (elementary), rated A; Castro Valley High School (high), rated A-. All sit in Castro Valley Unified School District. Attendance boundaries change — confirm with the district before relying on an assignment.

How does 20321 Sapphire St, Castro Valley, CA compare to other homes in Castro Valley 94546?

Among the 13,475 homes in Castro Valley 94546, it is worth more than 28% of them ($828,020 against a typical $989,959), its price per square foot is higher than 85% of them ($749 against a typical $627), it is bigger than 17% of them (1,106 ft² against a typical 1,540 ft²), its lot is bigger than 18% of them (0.12 ac against a typical 0.15 ac) and it is newer than 38% of them (1952 against a typical 1956). Measured against all of Alameda County, it is worth more than 34% 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 20321 Sapphire St, Castro Valley, CA?

The 2025 property tax bill for 20321 Sapphire St, Castro Valley, CA was $3,038. The county assessed it at $187,486.

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