Rent & Account Size

What it is

Every Solana account reserves a fixed number of bytes (data_length) chosen when it’s created, and must hold a minimum SOL balance proportional to that size to be rent-exempt. Below the threshold, an account would be subject to rent collection and eventually purged; at or above it, the account lives indefinitely.

Why it exists

Account data lives in validators’ memory and must be paid for. Rent exemption front-loads that cost: you deposit ~2 years of rent up front, and the account never gets collected. The deposit is refundable — close the account and the lamports go back to whoever you designate.

Byte layout

Rent isn’t a field inside the account; it’s a relationship between two header values:

The rent-exempt minimum is roughly:

rent_exempt_lamports ≈ (128 + data_length) bytes
                        × lamports_per_byte_year
                        × 2 years

The 128 is fixed per-account metadata overhead. As a rule of thumb it works out to about 0.00089 SOL for a 0-byte account plus roughly 0.00000696 SOL per additional byte, so an 82-byte Mint needs ~0.0014 SOL and a 165-byte Token Account ~0.002 SOL.

Where you see it

Every account-creation transaction funds the new account to its rent-exempt minimum. getMinimumBalanceForRentExemption(size) returns the exact figure for a given byte length.

Common gotchas

• Size is fixed at creation. You can’t grow an account later without realloc (which itself is capped per transaction and needs extra rent). Plan account space up front.
• Rent is a deposit, not a fee. It’s not consumed — it’s locked. Closing the account refunds the full lamport balance to the recipient you specify.
• Under-funding leaves the account collectible. An account below the rent-exempt minimum can be garbage-collected. Practically every account is created rent-exempt for this reason.
• The 128-byte overhead is real. A “0-byte” account still costs rent for 128 bytes of metadata. Tiny accounts aren’t free.
• SPL Token mints couldn’t reclaim rent until Token-2022. A closed-out SPL Mint stranded its rent forever; MintCloseAuthority fixed that for Token-2022.