Understanding the Cost of Living Index: What the Numbers Actually Mean
Published July 16, 2026
Cost of living indices show up everywhere - relocation guides, salary calculators, "best places to live" rankings - but most people have only a fuzzy idea of what the number actually represents. Here's the plain-English version.
100 is the anchor, not a target
On this site, and on most reputable cost of living indices, 100 represents the US national average. It's not "average" in the sense of "typical" or "recommended" - it's a mathematical anchor point. A city with an index of 130 costs approximately 30% more than that national average across the categories measured; a city at 80 costs about 20% less.
It's a weighted composite, not a single price
No single price tag captures "cost of living" - it's built by combining several categories, each weighted by how much a typical household spends on it. Our composite index weights housing at 30%, transportation and food at 15% each, utilities and healthcare at 10% each, and the remainder split across miscellaneous spending and taxes. That means a city that's dramatically cheaper on housing but average on everything else will still show a meaningfully lower overall index, since housing carries the heaviest weight.
Why your personal number might differ from the index
The weights above reflect a typical household's spending pattern, based on BLS Consumer Expenditure Survey data - not yours specifically. If you don't own a car, the transportation weight overstates your real exposure to that category. If you rent a small apartment instead of buying a median-priced home, the housing category may overstate your costs too. This is exactly why every city page shows the category breakdown, not just the composite score - use the categories that actually apply to your life and mentally down-weight the ones that don't.
Index numbers compare cities, they don't predict your budget
An index tells you that City A is roughly 20% more expensive than City B - it does not tell you that you personally need exactly 20% more income. Your actual costs depend on your household size, the neighborhood you choose within a city (a downtown loft and a suburban house in the same metro can have very different costs), and your lifestyle. Treat the index as a comparison tool, not a personal budget calculator.
How to use it correctly
- Compare the index, not the raw dollar figures, when judging relative affordability between cities.
- Check the category breakdown for the categories that matter most to your actual spending.
- Use our built-in salary calculator on any city page to convert the index difference into an actual dollar figure based on your real, current salary.
- When deciding between two specific cities, use a direct city vs. city comparison instead of eyeballing two separate pages.
Where the underlying numbers come from
Every figure behind our index is sourced from official public data - the US Census Bureau's American Community Survey for housing, income, and demographics, and the Bureau of Labor Statistics for wages. We never estimate or invent figures - see our About page for the full methodology.