The Situation

I have a Wise account for EUR and AUD.

Into the Wise AUD account I can easily (without fees) put money from an AUD bank account when needed. For most of my purchases I use the AUD account, but some online purchases I should pay with my EUR account in order to avoid conversion fees.

Now, I have received a larger amount in the EUR account which I won't us up in a year. So it makes sense to move the money (via the Wise AUD account) out of Wise into a an normal savings account to get some interest. But as said for some money it might make sense to be kept in the EUR account for the occasional case of low-amount online purchases in foreign Europe.

My Question

How can I create an easy way (algorithm/formula) to decide much money I should keep in the Wise EUR account?

Specific information

  • Interest rate of the AUD savings account: 1.35% p.a

  • Past purchases per year on the EUR account (as prediction): EUR 250

  • EUR amount in Wise account: EUR 3000

  • Wise fee per transfer out of Wise: approx. AUD 0.80.

  • Wise exchange rate: 1 EUR = 1.58 AUD plus approx. 0.4% fee

This means: Let's say I transfer

2,000 EUR.

Then I will at the end have

(2000 - 0.4%) * 1.58 - 0.8 = 3,146 AUD

transferred into my AUD Savings account.

Additional Idea

Is there maybe a standard way to find an answer here (some "optimisation" model)? Does possibly some (simple!) software offer a preset model for this kind of questions?

  • How much interest do the savings accounts earn? What’s the exchange rate? How much do you expect to spend this year from the EUR fund? It just might be simpler to make an educated guess based on past experience and forecasted spending.
    – RonJohn
    Jan 17, 2022 at 13:53
  • @RonJohn Thanks for chiming in! I have added specifics to the post. See above.
    – halloleo
    Jan 18, 2022 at 6:51
  • 1
    You can create a spreadsheet with multiple scenarios, and then graph that. But since the interest rate on savings is so low, I think it's simplest to decide how many years worth of purchases you want to keep in the Euro account. EUR1000 is four years worth. That seems high to me, but you might have other reasons not stated here.
    – RonJohn
    Jan 18, 2022 at 14:21
  • Your judgment helped, @RonJohn. I re-estimated my yearly spendings, did the projection and moved the money accordingly. Thanks!
    – halloleo
    Jan 28, 2022 at 11:51


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