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Longmont population

Longmont, Colorado had an estimated 100,109 residents on July 1, 2025, the 358th-largest city in the US. That is up 16% since the 2010 Census and up 39.9% since 2000.

LongmontColoradoPop. 100,109
Population, July 2025
100,109+1.2% since April 2020
People per sq mile
3,42129.3 sq mi of land
Median age
40.318.6% are 65 or older
Households with kids
24.6%with anyone under 18

Population by year, 2000 to 2025

60k70k80k90k100k2000: 71,56420002001: 74,6652002: 75,97320022003: 76,5732004: 77,69820042005: 78,6492006: 80,32020062007: 82,0242008: 83,78020082009: 85,2502010: 86,27020102011: 87,6602012: 88,94420122013: 90,2452014: 91,44820142015: 93,0902016: 94,05420162017: 94,5322018: 95,25120182019: 97,3162020: 98,90020202021: 99,7622022: 98,98820222023: 98,9902024: 99,60020242025: 100,1092025
Darker bars are the April 2000, 2010 and 2020 benchmarks; the rest are July 1 estimates. Source: US Census Bureau population estimates (intercensal 2000-2010, Vintage 2020 and Vintage 2025).
YearPopulationChangeBasis
2025100,109+509Estimate, July 1
202499,600+610Estimate, July 1
202398,990+2Estimate, July 1
202298,988-774Estimate, July 1
202199,762+862Estimate, July 1
202098,900+1,584April 2020 estimates base
201997,316+2,065Estimate, July 1
201895,251+719Estimate, July 1
201794,532+478Estimate, July 1
201694,054+964Estimate, July 1
201593,090+1,642Estimate, July 1
201491,448+1,203Estimate, July 1
201390,245+1,301Estimate, July 1
201288,944+1,284Estimate, July 1
201187,660+1,390Estimate, July 1
201086,270+1,0202010 Census (April 1)
200985,250+1,470Estimate, July 1
200883,780+1,756Estimate, July 1
200782,024+1,704Estimate, July 1
200680,320+1,671Estimate, July 1
200578,649+951Estimate, July 1
200477,698+1,125Estimate, July 1
200376,573+600Estimate, July 1
200275,973+1,308Estimate, July 1
200174,665+3,101Estimate, July 1
200071,564April 2000 estimates base

Year-to-year changes across 2010 and 2020 mix census counts with estimates, so small jumps at those years are partly method changes.

Frequently asked questions

What is the population of Longmont in 2025?

The Census Bureau estimates Longmont had 100,109 residents on July 1, 2025, making it the 358th-largest city in the US.

Is Longmont growing?

Yes. Longmont has grown 16% since the 2010 Census (86,270 people), and grown 1.2% since 2020.

What was the population of Longmont in 2000?

About 71,564 (the Census Bureau's April 2000 estimates base). By the 2010 Census it was 86,270.

How dense is Longmont?

Longmont has about 3,421 people per square mile of land (29.3 square miles).

More about Longmont

See cost of living, jobs and commutes in Longmont, Longmont weather by month, or every Longmont ZIP code. For the biggest cities in the country, see the largest US cities.