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Seiji

#9,565 in 2025Boys' name

Sincere, honest, true or pure, refined

Seiji has been given to 517 babies in the U.S. since 1914. In 2025 it ranked #9,565 of 13,926 boys’ names in use. Its peak year was 2007, with 19 recorded.

Babies named Seiji, 2025

1 in 414,000

Seiji over time, 1880–2025

Boys
0510152018801900192019401960198020002020

Based on births in the U.S. Babies given the name each year. Hover the chart — or focus it and use the arrow keys — for any year. Gaps mean the name was given fewer than 5 times that year; these counts are unpublished.

Seiji: meaning, origin, and history

Sincere, honest, true or pure, refined

Japanese

What Seiji means

Seiji means “sincere, honest, true or pure, refined”.

Origin, language, and formation

Seiji is used in English and Portuguese. Its origins include Japanese.

Seiji comes through Japanese せいじ.

American usage and historical context

In the United States, 517 boys were recorded with the name Seiji between 1914 and 2025. Its highest annual count was 19 in 2007; its best national rank was #2,563 in 1925.

Over 5 years its rank fell, from #7,948 in 2020 to #9,565 in 2025. Over 10 years its rank fell, from #7,432 in 2015 to #9,565 in 2025.

Sources & methodologyReferences, data & attribution

Meaning, origin, and language notes draw on the references below.

American popularity figures use published Social Security Administration records for this exact spelling. Counts below five for a name, sex, and year are omitted.

Wiktionary material is available under CC BY-SA 4.0.

How common is Seiji?

Everything below is computed from the 2025 data — the most recent year available.

Among all babies, 2025
1 in 414,000
8 of 3,315,165 births
Among boys only
1 in 213,000
<0.01% of boys
Rank, 2025
#9,565
of 13,926 boys’ names in use
Coin-flip room size
287,238 kids
Even odds of a second one

Where Seiji sits on the popularity scale

Rarest published (5 a year)#1 — Liam (20,818)

Chance at least one other child shares the name

If the other children were drawn at random from the 2025 national name distribution. Real classrooms cluster by region and community, so treat these as a floor, not a ceiling.

Class of 20Under 1%
Class of 30Under 1%
Grade of 100Under 1%
School of 500Under 1%

Put another way: gather 287,238 children born in 2025 and it's an even bet that one of them is another Seiji. In a class of 30 the chance is Under 1%.

When Seijis were born

Half of everyone ever recorded as Seiji was born before 2001 — so the typical Seiji is around 24 today.

Median birth year
2001
About 24 years old
Biggest decade
2000s
22.4% of all use
Born in the last 25 years
51.1%
A modern name
Recorded since 1950
405
People you could plausibly meet
Choose a decade

2000s — 22.4% of all recorded uses (116).

Is Seiji rising or falling?

Rank movement and count movement can disagree — the number of distinct names in use keeps growing, so a name holding a steady count still slides down the list. Both are shown.

Rank vs 1 year ago
+152
Places climbed
Rank vs 5 years ago
−1,617
Places dropped
Rank vs 10 years ago
−2,133
Places dropped
Births vs 10 years ago
0.73×
Fewer babies than then
Share of its own peak
42.1%
Peak was 2007 (19)
Years since peak
18
Years
Year-to-year steadiness
Volatile
31.9% average annual change
Best rank ever
#2,563
1925

Spellings of Seiji

Seiji is not the most common spelling — Kenji is, with 59.6% against Seiji's 5.5%.

Grouped by closeness of spelling (up to two letter changes), same sex, with a floor on all-time use. It catches Sophia/Sofia and Aiden/Ayden, and misses spellings that sound alike but look different, like Sean and Shawn.

Where Seiji is used

Across 1910–2025, Seiji was most concentrated in Hawaii — about 1 in 16,667 boys, against 1 in 290,307 across all states with data. It was least common in California (1 in —).

06 per 100,000

Most concentrated

  1. 1Hawaii1 in 16,667
  2. 2California1 in —

Shading is the share of that state's recorded boys given this name, not the raw count — otherwise the map would just show which states are biggest. Unshaded states have no published records for this period. U.S. birth records suppress state-year counts below 5; state counts therefore don't add up to the national total. Every state links to its full rankings. Seiji has too little recent state data to map, so this covers all years from 1910.

Seiji around the world

Where Seiji ranks in official birth records elsewhere in the world. Rankings only — the number of births isn’t comparable between places, so it isn’t shown.

  • England & Wales
    2012–2013
    #4,685
    in 2013
  • France
    2002–2024
    #6,617
    in 2024

Popularity data from Office for National Statistics and Institut national de la statistique et des études économiques. ONS data under Open Government Licence v3.0. INSEE data under Licence Ouverte / Etalab 2.0.

Seiji by the numbers

The raw record for each sex the name is used for.

As a boy's name

Rank in 2025
#9,565
Trend vs 5 yrs ago
Down 1,617
Best rank ever
#2,563
1925
Peak year
2007
19 that year
First recorded
1914
Last recorded
2025
All-time count
517
Count in 2025
8

Names similar to Seiji

Matched on shared beginnings and endings, similar length, and comparable popularity.

SeifSeiyaKeijiSeithSeichiSeikoSeibertSeiichiEijiSeikiSeituSeigoSeikichiSeinSeidSeidonSei

Sibling names for Seiji

Names from the same era and popularity tier — the two things that make a sibling set feel deliberate — skipping lookalike spellings and shared initials.

Explore around Seiji

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