Below average beats guessing
A rate on its own is meaningless: is 5.4 reais to the euro good? The honest answer is another question — good compared to what? The practical comparison is the rolling average of the last ninety days. When today's rate buys you more of the currency you need than the recent average would, you are exchanging on sale. When it buys less, you are paying a premium that patience might remove.
This is deliberately humble math. It does not claim the rate will not get even better tomorrow — it claims that beating your own recent baseline is the only version of "timing the market" that a traveler can systematically win.
Volatility decides how to split
The second number that matters is how jumpy the pair has been. A calm pair drifting in a two-percent band rewards a single exchange on a below-average day. A volatile pair can move more in a week than the average saves you in a month — there, splitting the exchange into two or three tranches trades a little upside for a lot of protection.
- Calm pair, rate below average: exchange the bulk now, keep a small remainder for the trip itself.
- Volatile pair: split into tranches on separate below-average days; never exchange everything at an above-average rate unless departure forces it.
- Always leave a card-payable buffer — the best rate you will ever get on the last 10% is the one you never had to lock in.
Know what you actually need first
None of this works without the denominator: how much of each currency the trip requires. A plan that prices hotels in euros, museums in koruna, and dinners in forints tells you exactly what to watch and how much of it to move — which is why Pardal computes a per-currency breakdown from every Report and watches the rates for those currencies specifically.
The alert you want is not "the euro moved." It is "the €840 your Lisbon stay needs is 2.3% cheaper than its 90-day average today." One number is news; the other is a decision.