Seattle Population 2024 Forecaster. Seattle’s population grew by 21% to 737,015 people and king county swelled by more than 300,000 residents since 2010, according to new u.s. Seattle has a 2024 population of 759,915.

These data (statistics and projection) are based on information from the united nations and census on the assessment and forecasting of the seattle city population. That’s an additional 240,000 or so residents over the next 22 years.