Why do tax rate differences matter so much?

The combined effective tax rate (federal + state + local) varies more than people realize. A $200K earner in SF pays roughly 37% effective; in Austin TX it's roughly 24%. That's a 13-percentage-point swing — $26K/year on the same gross income before any cost-of-living difference. Texas/Florida/Washington/Nevada/Tennessee/South Dakota/Alaska have no state income tax. New Hampshire taxes only interest and dividends. California, NY, NJ, MA, CT, OR have the highest top marginal rates.

Where does the COL index actually come from?

Numbeo and Expatistan both compile COL indexes from user-submitted prices on standardized baskets (apartment rent, restaurant meals, groceries, transport, utilities). Numbeo tends to be more current; Expatistan more methodologically transparent. We use Numbeo-style numbers in the calculator (US average ≈ 100, NYC ≈ 175, SF ≈ 190). For non-US cities, both Numbeo and BCG's CityCompass report give similar results within ±10%. The numbers are average — your specific lifestyle determines what fraction of the average actually applies to you.

What about state tax on remote work — does CA chase you across the border?

Generally no, but there are nuances. If you genuinely move (sell or rent out CA home, register vehicles in new state, change driver license, register to vote, healthcare provider in new state), CA accepts the move and stops withholding after about 6 months. The 'hide-and-seek' cases where CA disputes residency happen mostly to people who keep substantial CA ties — often returning multiple times per year, keeping a CA address for some accounts, etc. The conservative pattern: full break, full year out, then return for visits but not domicile. Consult a CPA before December if you're moving mid-year — the part-year resident return is the trickiest filing.

How do I model the 'still want to live like an SF person' lifestyle creep in Austin?

Add 10–25% to expected new-city expenses. The mechanism: in SF you naturally constrain consumption because everything's expensive (you don't go to bars 4 nights a week because rounds cost $80+). In Austin, the same lifestyle costs less, but you typically expand consumption to recover some of the disposable-income gap — bigger apartment because you can afford it, more eating out because dinners are $40 instead of $80, kid in private school you couldn't have afforded in SF. The gap is real but smaller than the index difference suggests. Conservative modeling: assume new-city actual expenses are 80% of theoretical COL-adjusted, not 100%.

$200K SF to Austin: $36K/Year Savings Boost, $510K Over 10 Years

The Move That Tech Twitter Made Famous

Sarah is a senior engineer at a tech company in SF. $200K total comp, married to a full-remote partner, no kids yet. They’ve been considering Austin for two years — friends moved during 2021, the company just confirmed her role can be fully remote, and she ran the numbers in a 30-minute Sunday-afternoon session.

Here’s what the calculator says:

Metric	SF (current)	Austin (proposed)
Annual gross	$200,000	$200,000
Effective tax rate	37% (federal + CA + SF local)	24% (federal + TX 0%)
Annual take-home	$126,000	$152,000
Annual expenses	$94,500 (75% of take-home)	$54,000 (COL adjusted)
Annual savings	$31,500	$98,000
Savings rate	25%	64%
Savings boost	—	+$66,500/year
10-year wealth gap (7% real return)	—	+$919K

These are the on-paper numbers. They look life-changing. The honesty correction below brings them down to earth.

The Three Levers

The savings rate change comes from three independent inputs that compound:

1. Tax rate delta: $26K/year. The 13-point spread (37% → 24%) on $200K gross is $26K of extra take-home, before any cost-of-living move. This is the cleanest, most reliable lever — federal brackets stay the same, state tax disappears, FICA caps don’t move. Texas and similar no-income-tax states make this lever maximum.

2. Cost-of-living delta: $40K/year. SF COL index ≈ 190, Austin ≈ 110 (about 58% of SF). At $94K of SF-anchored expenses, COL-adjusting to Austin yields $54K — a $40K reduction. The biggest single component is housing: a 1BR in SF averages $3,500/mo, in Austin it’s $1,800. Groceries and utilities scale less aggressively (typically 30-50% cheaper rather than 50%+).

3. Compounding: $919K → $510K (after honesty correction). The $66.5K/year savings boost compounded at 7% real return over 10 years yields $919K. This is the financial-planning textbook number. Reality is closer to $510K because lifestyle creep, transition costs, and taxes recapture some of the boost. More on this below.

Where this scenario doesn’t apply

The framework above assumes a few things. Counter-examples worth flagging:

Company-mandated pay cuts on relocation. Many companies adjust pay by location (Meta, Twitter pre-2022). A $200K SF role often becomes $170K in Austin via the company’s geo-cost adjustment. The geo-arbitrage tool assumes constant gross income — pair with the Remote Pay Cut tool when the company applies a discount.
Two-income households. If your partner has a non-remote job in SF, the move may force a job change for them. Career-disruption risk often dominates the financial math for dual-income couples.
Already-low-cost current city. Moving from Austin to Memphis still has positive geo-arbitrage but the magnitude is small ($5–15K/year) and rarely worth the disruption. The math is best when current city is in the top-10 most expensive.
Strong local network. SF/NYC have professional networks that compound in ways geo-arb can’t capture. If you’re in early career and would lose access to a startup ecosystem you’re actively benefiting from, the wealth gap may invert.
Mid-school-age kids. School-district moves disrupt friend groups, extracurriculars, college trajectories. The financial math sometimes works; the family math often doesn’t.
Rental ownership in current city. If you own a home in SF and rent in Austin, you might keep the SF house as a rental and capture both COL arbitrage AND continued SF appreciation. The math gets more complex but often more favorable.

The Honesty Correction

The $919K theoretical 10-year wealth gap comes down to about $510K under realistic assumptions:

Adjustment	Impact	Why
Lifestyle creep (+15% expenses in new city)	-$130K	”Live like SF, pay Austin” — bigger apartment, more dining out
One-time relocation costs ($15K)	-$30K	Lost compounding on first-year cash drag
Career disruption risk (10% probability)	-$90K	Probability-weighted: company changes remote policy, role eliminated
Healthcare cost normalization	-$20K	TX healthcare is sometimes cheaper, sometimes not — net wash
Tax filing transition complexity	-$10K	Part-year resident filing in year 1
Remaining real wealth gap (10y)	$639K	Conservative estimate
Plus 20% buffer for unknowns	-$130K
Realistic 10y wealth gap	~$510K	What Sarah should plan around

The honest framing: the move probably nets $50K/year in realized savings (not $66K theoretical), and over 10 years compounds to $500K-650K. Still life-changing. Just not “double your wealth in 10 years” magnitude.

Where the calculator falls short

Single point in time. We assume static incomes and tax rates. Real careers grow; tax laws change.
No housing complications. Selling a CA home in a soft market while buying TX in a hot market changes the math materially.
No state-specific deduction nuances. CA has high state SALT but the federal SALT cap of $10K caps the deduction. TX has property tax of 2-3% (high) which partly offsets the no-income-tax benefit for homeowners.
No partner-employment analysis. A two-income household needs to model both careers simultaneously.
No school district pricing for families with kids. Quality schools in TX often cost $20-40K/year private vs SF public being mediocre but free.
Currency risk for international moves. Same gross USD but local-currency expenses fluctuate.

What to actually do

Run the calculator with conservative inputs. Use 80% of theoretical COL adjustment, not 100%. Use the high end of new-city tax estimates.
Validate with 90 days of test residency. Rent monthly Airbnb in target city for 90 days, work fully remote, track actual expenses. The number you observe is more accurate than any index.
Get a CPA quote. A 60-minute session with a multistate CPA ($300-600) often saves more than the calculator number suggests, especially for the year-of-move filing.
Pair with other calculators. Moving Cost for one-time costs, FIRE Calculator for retirement-acceleration impact, Personal Inflation for individual cost basket sensitivity.
Don’t decide on math alone. Career networks, family proximity, social capital, weather, and city-fit dominate financial outcomes for most people. Use the calculator to confirm the math isn’t blocking you, not as the deciding voice.

Open the Geo-Arbitrage Calculator → and run your specific city pair. Pair with the Moving Cost calculator to factor in one-time relocation costs, and the Remote Work Savings calculator for the same-city alternative if a full move isn’t feasible.