2000
#9,401
National surname rank
Recorded bearers 3,176
First available Census row
Per 100,000 1.18
Rare Last name
Castelli
An Italian topographic surname referring to someone who lived near or in a castle.
According to the 2020 US Census Bureau surname tables, roughly 3,408 Americans carry the last name Castelli. That puts it at #10,315 in the national surname ranking, appearing at a frequency of 0.99 per 100,000 people (about 1 in 100,573 residents).
This page is the full Name Census profile for the Castelli surname. You will find the Census Bureau frequency data, a multi-census history view, an ancestry and ethnicity breakdown based on self-reported demographics, the name's meaning and origin where available, and answers to the most common questions people ask about this surname.
For British records, Name Census UK has a British surname profile for Castelli with 1881 census detail, origin facts and modern UK distribution where available.
Bearers in the US
3.4K
1 in 100,573
Census rank
#10,315
2020 decennial data
Per 100,000
1.0
Frequency rate
Recorded bearers
3.0K
rare in the US
Popularity narrative
The Census Bureau recorded 2,972 bearers of the surname Castelli in its 2020 decennial surname file. At a rate of 0.99 per 100,000 residents, it holds the 10315th position in the national surname ranking.
Among Census respondents with the surname Castelli, the largest self-reported group is White at 91.2%. The next largest groups are Hispanic (5.7%) and Two or More Races (2.0%).
Origin
Meaning and origin of Castelli
The surname Castelli originated in Italy during the medieval period, derived from the Italian word "castello," meaning castle or fortified dwelling. It was initially used as a descriptive name for someone who lived near or worked in a castle, or possibly as an occupational name for a castle guard or builder.
In the early days, the name was commonly found in various regions of central and northern Italy, including Tuscany, Umbria, and Lombardy, where castles and fortified towns were prevalent. The earliest recorded instances of the name can be traced back to the 12th and 13th centuries, with variations in spelling such as Castellis, Castelli, and Castelli.
One of the earliest notable individuals with the surname Castelli was Giovanni Battista Castelli, an Italian mathematician and philosopher born in 1577 in Brescia, Lombardy. He was a prominent figure in the scientific revolution and a close collaborator of Galileo Galilei.
Another prominent bearer of the name was Benedetto Castelli, born in 1578 in Brescia, Lombardy. He was a renowned hydraulic engineer and mathematician, known for his pioneering work on the study of fluid mechanics and the development of the scientific method.
In the 14th century, the Castelli family was documented as a noble family in the city of Siena, Tuscany. One of their members, Niccolò Castelli, born in 1347, was a renowned poet and humanist scholar.
The surname Castelli also gained prominence in the arts, with notable figures such as Bernardo Castelli, an Italian painter born in 1557 in Genoa, whose works can be found in various churches and galleries across Italy.
Francesco Castelli, born in 1593 in Milan, was a celebrated architect and engineer known for his contributions to the design and construction of numerous churches, palaces, and fortifications in the region of Lombardy.
As the name spread across Italy, it was also adopted by families in other regions, leading to further variations in spelling and pronunciation. However, the connection to castles and fortified dwellings remained a common thread throughout its history.
Demographics
Ancestry and ethnicity for Castelli
Among Census respondents with the surname Castelli, the largest self-reported group is White at 91.2%. The next largest groups are Hispanic (5.7%) and Two or More Races (2.0%).
The bar chart below shows how Castelli bearers described their own race and ethnicity on the 2020 Census form. The Census Bureau groups responses into six broad categories: White, Black or African American, Hispanic or Latino, Asian and Pacific Islander, American Indian and Alaska Native, and Two or More Races. When a category has too few respondents for a given surname, the Bureau suppresses the figure to protect individual privacy, which is why some names show fewer than six slices.
Percentages are shown for every Census year so the breakdown stays comparable over time. When the source file also includes raw headcounts, Name Census shows those alongside the percentages in the legend.
Keep in mind that these are self-reported numbers. A person's surname does not determine their race or ethnicity, and the distribution you see here reflects the specific population who happened to carry the Castelli surname at the time of the 2020 Census, not any inherent property of the name itself.
- White91.2% · 2,710
- Hispanic or Latino5.7% · 170
- Two or more races2.0% · 59
- Asian and Pacific Islander0.8% · 23
- Black or African American0.3% · 9
- American Indian and Alaska Native0.0% · 1
Timeline
Historical Census data for Castelli
Castelli appears in 3 published Census surname files: 2000, 2010, 2020. The cards below show how the name's rank and bearer count changed across each release.
2010
#9,834
National surname rank
Recorded bearers 3,292
+116 bearers (+3.7%)
Per 100,000 1.12
Rank movement Down 433 places
2020
#10,315
National surname rank
Recorded bearers 2,972
-320 bearers (-9.7%)
Per 100,000 0.99
Rank movement Down 481 places
| Year | Rank | Count | Per 100K | Count change | Rank change |
|---|---|---|---|---|---|
| 2000 | #9,401 | 3,176 | 1.18 | First available Census row | First available Census row |
| 2010 | #9,834 | 3,292 | 1.12 | +116 bearers (+3.7%) | Down 433 places |
| 2020 | #10,315 | 2,972 | 0.99 | -320 bearers (-9.7%) | Down 481 places |
For 2020, the Census Bureau published race and Hispanic-origin columns as counts rather than percentages. Name Census converts those counts back into shares so the ancestry section stays comparable with the older surname files.
Year on year
2010 vs 2020 Census
How has the Castelli surname changed between Census years? The chart shows bearer count side by side, and the table compares rank, count, and frequency.
Census year comparison
20102020
| Metric | 2010 | 2020 | Change |
|---|---|---|---|
| Rank | #9,834 | #10,315 | -4.9% |
| Count | 3,292 | 2,972 | -9.7% |
| Per 100K | 1.12 | 0.99 | -11.2% |
Between the 2010 and 2020 Census, the number of Castelli bearers went from 3,292 to 2,972 (-9.7% change). The surname moved down 481 positions in the national ranking, going from #9,834 to #10,315.
FAQ
Castelli surname: questions and answers
How many people in the U.S. have the surname Castelli?
Name Census estimates that about 3,408 living Americans carry the surname Castelli. Using the current population baseline, that works out to roughly 1 in 100,573 residents.
How common is Castelli?
Castelli ranks #10,315 in the 2020 Census surname tables and is classified on this site as "Rare." The Census recorded the name at a frequency of 0.99 per 100,000 residents, which is about 1 people out of every 100,000.
How many people with this surname were counted in the Census?
The raw 2020 Census file counted 2,972 people with the surname Castelli. That is different from the site's living-bearer estimate (3,408), which projects the surname's present-day count by applying the Census frequency rate to the current U.S. population.
What does 0.99 per 100,000 actually mean?
It is the Census Bureau's normalized frequency measure. A rate of 0.99 per 100,000 means that if you picked a random group of 100,000 U.S. residents, you would expect about 1 of them to have the surname Castelli.
Has Castelli become more or less common over time?
Between 2010 and 2020, the surname Castelli went from 3,292 recorded bearers to 2,972. That is a decrease of 320 (-9.7%). In the national ranking it fell from #9,834 to #10,315.
What does the Census say about the background of Castelli?
Among Census respondents with the surname Castelli, the largest self-reported group is White at 91.2%. The next largest groups are Hispanic (5.7%) and Two or More Races (2.0%). These figures come from the 2020 Census Bureau surname tables, based on how respondents described their own race and ethnicity.
Which group reports this surname most often?
White is the largest self-reported group for the surname Castelli in the 2020 Census, accounting for 91.2% (2,710 people in the source table).
What is the full ancestry breakdown?
Castelli appears across multiple self-reported groups in the Census data. The largest shares in the 2020 file are White (91.2%), Hispanic (5.7%), Two or More Races (2.0%). For 2020, the source file also published raw headcounts for each group, which is why this page can show both percentages and counts in the ancestry section.
Is this page using the latest Census data?
Yes. This page is using the latest surname file currently loaded on Name Census, which is 2020. The historical section above also keeps any older Census surname entries we have for Castelli (2000, 2010, 2020).
Does the Census include every surname?
No. The Census Bureau only publishes surnames that appeared at least 100 times in a given decennial Census. That means very rare surnames are excluded entirely, and a surname can appear in one Census release but disappear from a later one if it falls below the reporting threshold.
Why don't the ancestry percentages always add up to exactly 100%?
There are two main reasons: rounding and suppression. The Census Bureau rounds published values, and it may suppress very small cells to protect privacy. For 2020, the Bureau also published raw group counts rather than direct percentages, so Name Census converts those counts back into shares for comparability across census years.
What does Castelli mean?
An Italian topographic surname referring to someone who lived near or in a castle. The fuller origin note on this page goes into more detail.
Where does the surname data come from?
All surname statistics on Name Census are drawn from the US Census Bureau's decennial surname frequency tables. These files list every surname that appeared 100 or more times in the 2020 Census, along with a count, a per-100,000 rate, and a self-reported demographic breakdown. You can read the full explanation on our methodology page.
How does Name Census estimate living bearers?
For surnames, Name Census does not age cohorts the way it does for first names. Instead, it takes the Census Bureau's published frequency for Castelli (0.99 per 100,000) and applies that rate to the current U.S. resident population to estimate how many living Americans have the surname today.
How many people are called Castelli?
See how many people have the surname Castelli on HowManyOfMe.org, our sister site built around that single question.