FX-Aware Savings Rate Calculator
Your savings rate, without the FX lies.
Most FIRE calculators use change-in-net-worth ÷ income as a proxy for savings rate. For anyone with multi-currency assets, that number is a mix of real saving, market returns, and FX movement, and you can’t tell which is which. This separates them.
Reported rate
43.8%
ΔNW ÷ income
True savings rate
40.0%
(income − spending) ÷ income
The gap is mostly market growth, not FX — investment returns added ~3.8 percentage points to your reported rate.
Where your net-worth change came from
Total change in net worth
NOK 350,000
Real savings (income − spending)
NOK 320,000
FX impact
NOK 0
Investment returns (residual)
NOK 30,000
Real-savings vs FX vs returns · monthly · per-account · no estimation needed
The lie hidden in the standard formula
Open any FIRE blog and you’ll see savings rate defined two different ways without anyone flagging the difference. The textbook version: (income − spending) ÷ income. The practical proxy people use: (net worth at end of year − net worth at start) ÷ income. For a single-place, single-currency life, the two converge. For everyone else, they diverge, sometimes badly.
The proxy bakes three things together: how much you actually saved, how much your investments grew or shrank, and, for multi-currency lives, how much your net worth moved because of exchange rates that have nothing to do with anything you did. Three completely different stories, one number.
The decomposition this calculator does
ΔNW = (income − spending) + FX impact + investment returns
└── real savings ──┘ └ user est ┘ └─── residual ────┘
reported_rate = ΔNW ÷ income × 100
true_rate = (income − spending) ÷ income × 100Real savings comes from the textbook definition: income minus spending, no inference. The FX impact is what you estimate (positive if your foreign-currency assets appreciated in your display currency, negative if they didn’t). What’s left after pulling those out is everything else: investment returns, valuation changes, fees.
If you don’t hold meaningful foreign-currency assets, leave FX impact at 0; the calculator collapses to a clean “real savings vs. market returns” split, which is still more honest than the headline rate.
How to estimate your FX impact
For each foreign-currency holding, multiply the balance by (new rate − old rate) in your display currency. If you held 10,000 USD all year and USD/EUR went from 0.92 to 0.87, the FX impact in EUR is 10,000 × (0.87 − 0.92) = −500 EUR. A few quick estimates across your holdings sum into the figure you enter above. The full app does this automatically from every monthly check-in: no estimation needed.
What this calculator deliberately doesn’t do
It can’t look at your accounts, so it can’t compute FX impact for you. It treats one year (or one period) as a single block: no within-period dynamics, no per-month volatility. And it’s only as honest as the FX-impact estimate you enter; lazy estimation gives lazy results.
What the full version adds
- FX impact computed automatically from every monthly check-in: no estimation.
- Per-currency breakdown: see which currencies flattered and which hurt.
- Trailing 12-month rolling savings rate, decomposed every month.
- Connects to FIRE projections: the years-to-FI math runs on true savings, not the misleading proxy.
Waitlist open. Cohorts onboarding now; the next opens before public launch. We’ll be in touch within a week of signup. Join the waitlist →
Go deeper: Lesson: FX Attribution, Real Growth vs Currency Luck →
More tools: Currency Conversion Cost → · FIRE Number → · Emergency Fund → · Read: your savings rate is half FX →
How we think about the numbers behind every figure: The method →
A calculator answers one question. fjordFIRE keeps the whole picture updated every month.