How We Calculate Name Rarity

The data

• First names: the U.S. Social Security Administration national baby-name data, public domain, covering every name given to at least 5 U.S. babies in a year from 1880 to 2024. That is 372,009,150 births across 104,819 names.
• Last names: the U.S. Census Bureau 2010 surname file, public domain, covering 162,253 surnames held by at least 100 people, 266 million people in total.

Both datasets ship with the site and run entirely in your browser. Nothing you type is uploaded.

The formula

For a first name, rarity is:

• 1 in X where X is the total births on record divided by the number of births with that name.
• All-time rank is the name's position when every name is sorted from most to least births.
• Share of people is the same thing as a percentage.

Surnames use the identical idea against the Census population instead of birth records. Every formula lives in one small module that is checked against known answers before each release, so the numbers on the site are the numbers the build verified.

The tiers

Tier	How many share the name
Very Common	more than 1 in 200 people
Common	about 1 in 200 to 1 in 2,000
Uncommon	about 1 in 2,000 to 1 in 20,000
Rare	about 1 in 20,000 to 1 in 200,000
Very Rare	about 1 in 200,000 to 1 in 2 million
Ultra Rare	rarer than 1 in 2 million

Honest limits

• These are counts of recorded names, not people alive today. A name given in 1920 counts the same as one given last year.
• The SSA hides any name given to fewer than 5 babies in a year, so the rarest names are not listed and show as "too rare to count."
• Each spelling is counted on its own. Different spellings of the same spoken name are not combined.
• Surname data is a 2010 snapshot and does not include names held by fewer than 100 people.