I'd like to use getMinimumBalanceForRentExemption. With that said, it expects a parameter of the size of the data account. I'd like to know if there's a way to get the estimate size of an account or whether I have to calculate it by hand.

In my rust code, I use use std::mem::size_of to get the size of a struct. Anything similar in the client side which is the one setting the rent budget or maybe something similar in the IDL?

1 Answer 1


Yes there is:

const program = anchor.workspace.MyProgram as Program<MyProgram>;
const myAccountSize = program.account.myAccount.size;
console.log('Size', myAccountSize);

Note that size also includes the anchor discriminator, so it will be 8 bytes bigger than you might expect.

  • If you are allocating space for the rent-free exception, you do have to include those 8 bytes, so it would be appropriate to use directly for OP's purposes.
    – Whiteseal
    Commented Mar 20 at 5:57
  • Absolutely - I included this just as an FYI, as otherwise it might come as a surprise that an account holding e.g. a u32 would return 12 with .size instead of the more intuitive 4
    – Ahri
    Commented Mar 20 at 6:05

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