2000
#5,629
National surname rank
Recorded bearers 5,655
First available Census row
Per 100,000 2.10
Rare Last name
Koski
A Finnish toponymic surname referring to someone living near rapids or a waterfall.
According to the 2020 US Census Bureau surname tables, roughly 5,813 Americans carry the last name Koski. That puts it at #6,452 in the national surname ranking, appearing at a frequency of 1.70 per 100,000 people (about 1 in 58,963 residents).
This page is the full Name Census profile for the Koski 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 Koski with 1881 census detail, origin facts and modern UK distribution where available.
Bearers in the US
5.8K
1 in 58,963
Census rank
#6,452
2020 decennial data
Per 100,000
1.7
Frequency rate
Recorded bearers
5.1K
rare in the US
Popularity narrative
The Census Bureau recorded 5,069 bearers of the surname Koski in its 2020 decennial surname file. At a rate of 1.70 per 100,000 residents, it holds the 6452nd position in the national surname ranking.
Among Census respondents with the surname Koski, the largest self-reported group is White at 92.1%. The next largest groups are Two or More Races (2.9%) and Hispanic (2.6%).
Origin
Meaning and origin of Koski
The surname Koski originated from Finland, with the earliest recorded examples dating back to the 16th century. It is derived from the Finnish word "koski," which means "rapids" or "waterfall," indicating that the name likely referred to a person who lived near a fast-moving stream or waterfall.
Koski is a common Finnish place name, and many early instances of the surname are found in connection with these locations. For example, in the parish records of Tammela, Finland, there are references to individuals with the surname Koski as early as the mid-1500s.
During the 17th and 18th centuries, the surname Koski appeared in various historical records and documents across Finland. One notable example is the Vanha Suomen Kartasto, a collection of old maps and cadastral records from the 17th century, which includes mentions of individuals and families with the Koski surname.
In the 19th century, several individuals with the surname Koski gained recognition in various fields. Juho Koski (1824-1890) was a Finnish writer and journalist who contributed to the development of Finnish literature. Kaarlo Koski (1847-1928) was a prominent Finnish architect known for his work on several churches and public buildings in Helsinki.
Other notable individuals with the surname Koski include Antti Koski (1826-1883), a Finnish politician and member of the Finnish Senate, and Yrjö Koski (1911-2003), a Finnish artist and sculptor whose works were exhibited throughout Europe and the United States.
The surname Koski has also been found in historical records from other Nordic countries, such as Sweden and Norway, where it may have been adopted by Finnish immigrants or derived from similar geographical features.
Demographics
Ancestry and ethnicity for Koski
Among Census respondents with the surname Koski, the largest self-reported group is White at 92.1%. The next largest groups are Two or More Races (2.9%) and Hispanic (2.6%).
The bar chart below shows how Koski 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 Koski surname at the time of the 2020 Census, not any inherent property of the name itself.
- White92.1% · 4,667
- Two or more races2.9% · 149
- Hispanic or Latino2.6% · 131
- Asian and Pacific Islander1.2% · 63
- American Indian and Alaska Native0.7% · 37
- Black or African American0.4% · 22
Timeline
Historical Census data for Koski
Koski 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
#6,424
National surname rank
Recorded bearers 5,288
-367 bearers (-6.5%)
Per 100,000 1.79
Rank movement Down 795 places
2020
#6,452
National surname rank
Recorded bearers 5,069
-219 bearers (-4.1%)
Per 100,000 1.70
Rank movement Down 28 places
| Year | Rank | Count | Per 100K | Count change | Rank change |
|---|---|---|---|---|---|
| 2000 | #5,629 | 5,655 | 2.10 | First available Census row | First available Census row |
| 2010 | #6,424 | 5,288 | 1.79 | -367 bearers (-6.5%) | Down 795 places |
| 2020 | #6,452 | 5,069 | 1.70 | -219 bearers (-4.1%) | Down 28 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 Koski 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 | #6,424 | #6,452 | -0.4% |
| Count | 5,288 | 5,069 | -4.1% |
| Per 100K | 1.79 | 1.70 | -5.3% |
Between the 2010 and 2020 Census, the number of Koski bearers went from 5,288 to 5,069 (-4.1% change). The surname moved down 28 positions in the national ranking, going from #6,424 to #6,452.
FAQ
Koski surname: questions and answers
How many people in the U.S. have the surname Koski?
Name Census estimates that about 5,813 living Americans carry the surname Koski. Using the current population baseline, that works out to roughly 1 in 58,963 residents.
How common is Koski?
Koski ranks #6,452 in the 2020 Census surname tables and is classified on this site as "Rare." The Census recorded the name at a frequency of 1.70 per 100,000 residents, which is about 2 people out of every 100,000.
How many people with this surname were counted in the Census?
The raw 2020 Census file counted 5,069 people with the surname Koski. That is different from the site's living-bearer estimate (5,813), which projects the surname's present-day count by applying the Census frequency rate to the current U.S. population.
What does 1.7 per 100,000 actually mean?
It is the Census Bureau's normalized frequency measure. A rate of 1.70 per 100,000 means that if you picked a random group of 100,000 U.S. residents, you would expect about 2 of them to have the surname Koski.
Has Koski become more or less common over time?
Between 2010 and 2020, the surname Koski went from 5,288 recorded bearers to 5,069. That is a decrease of 219 (-4.1%). In the national ranking it fell from #6,424 to #6,452.
What does the Census say about the background of Koski?
Among Census respondents with the surname Koski, the largest self-reported group is White at 92.1%. The next largest groups are Two or More Races (2.9%) and Hispanic (2.6%). 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 Koski in the 2020 Census, accounting for 92.1% (4,667 people in the source table).
What is the full ancestry breakdown?
Koski appears across multiple self-reported groups in the Census data. The largest shares in the 2020 file are White (92.1%), Two or More Races (2.9%), Hispanic (2.6%). 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 Koski (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 Koski mean?
A Finnish toponymic surname referring to someone living near rapids or a waterfall. 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 Koski (1.70 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 Koski?
If you just want to know how many people are called Koski, HowManyOfMe.org gives you the headline number in one glance.