Cost of living calculator: how to compare cities accurately
Most cost-of-living calculators give you a single index number and call it done. That's fine for a rough sanity check — but if you're actually deciding whether to take a job in a new city, you need to break the number down by category and weight it against your own spending. Here's how.
The core formula
To keep the same lifestyle in a new city, use the ratio of the two cities' cost-of-living indexes:
Required salary = current salary × (new city COL / old city COL)
Example: you earn $95,000 in Austin (index 105) and you're weighing a move to Seattle (index 172).
$95,000 × (172 / 105) ≈ $155,600
Anything below ~$155k in Seattle is a real-terms pay cut, even if the offer looks bigger on paper.
Step 1 — Break the index into categories
A single index number hides the truth. Split it into the four categories that drive 90% of the gap between cities:
Housing (rent or mortgage)
Usually the largest gap — often 2–3× between coastal and mid-size cities. Use current listings for a specific neighborhood, not a metro-wide average.
Taxes
State and local income tax, property tax, and sales tax. A no-income-tax state can offset a higher rent bill; a high property tax can erase it again.
Groceries & dining
Smaller absolute gap but consistent — coastal cities run 15–25% above the national average. Adjust for how often you eat out.
Transport
Car ownership vs. transit changes the answer more than any index will show. A $650/month car payment plus insurance can outweigh a lower rent.
Step 2 — Weight by your own spending
Standard indexes assume an average household. If housing is 45% of your budget (typical for renters in high-cost cities) but the index weights it at 30%, the index understates your real gap. Multiply each category's ratio by your actual share of spending, then sum:
Personal COL ratio = 0.45 × (new rent / old rent) + 0.15 × (new taxes / old taxes) + 0.15 × (new groceries / old groceries) + 0.10 × (new transport / old transport) + 0.15 × 1.0 (everything else, held constant)
Step 3 — Worked example: Austin → Seattle
| Category | Austin | Seattle | Ratio |
|---|---|---|---|
| Rent (1BR) | $1,700 | $2,400 | 1.41 |
| State income tax | $0 | $0 | 1.00 |
| Groceries | $450 | $540 | 1.20 |
| Transport | $700 | $350 | 0.50 |
| Weighted personal COL | ≈ 1.19 |
Your personal cost of living is 19% higherin Seattle — not the 64% the raw index implies — because you'll ditch the car and neither state charges income tax. A $95k → $115k offer would actually be a small real-terms raise.
Common mistakes to avoid
- • Using metro-wide averages when you'll live in a specific neighborhood — rents can vary 2× inside the same city.
- • Ignoring taxes — a state income tax of 9% is worth ~$8,500/year on a $95k salary.
- • Forgetting one-time costs — moving, security deposits, and new furniture can easily run $10k+.
- • Comparing gross salary only — always compare take-home pay after taxes and health insurance.
Run the numbers automatically
FuturePath does all of this for you — live city-level cost of living, state taxes, and a full lifetime forecast — in about 30 seconds.
FAQ
What is a cost of living index?
A weighted price comparison of a fixed basket of goods across cities, with a base city set to 100. It's a starting point, not a personal answer.
How much more salary do I need to move?
Multiply your current salary by the ratio of the two cities' indexes for a first-pass number, then re-do the math weighted to your actual spending (rent, taxes, transport) for the real answer.
Why do calculators disagree?
They weight housing, taxes, and transport differently. If a calculator doesn't let you plug in your actual rent, it will understate the gap for anyone moving into a high-cost city.