Skip to main content

Transaction Fees

Transaction fees on Cardano are deterministic and predictable, calculated using a simple linear formula based on transaction size and computational resources required. This approach ensures users can calculate exact fees before submitting transactions, avoiding the unpredictable fee spikes seen on other blockchains.

Fee Structure and Formula​

Cardano uses a straightforward fee calculation: fee = a × size(tx) + b

Where:

  • a: Protocol parameter reflecting the cost per byte of transaction data (currently 44 lovelace/byte)
  • b: Fixed base fee applied to every transaction regardless of size (currently 155,381 lovelace)
  • size(tx): Transaction size in bytes

Transactions with native tokens, metadata, or multiple outputs are larger and cost more. Smart contract transactions add script execution fees on top.

note

Protocol parameters change through on-chain governance. Query current values with cardano-cli query protocol-parameters or via your API provider.

Protocol Parameters and Economic Security​

Both parameters a and b serve crucial economic and security purposes:

Parameter a covers the resource costs of processing and storing larger transactions. As transaction size increases, more computational and storage resources are required, making this scaling factor essential for covering operational costs.

Parameter b provides a base security layer against economic attacks, particularly Distributed Denial-of-Service (DDoS) attacks. By requiring a minimum fee regardless of transaction size, it becomes prohibitively expensive for attackers to flood the network with millions of small transactions.

Fee Distribution Model​

Unlike many blockchains where fees go directly to block producers, Cardano uses a unique pooled distribution system. Transaction fees are collected and distributed among all stake pools that produced blocks during an epoch, regardless of which specific pool processed each transaction. This approach promotes network stability and fair reward distribution.

Economic Attack Prevention​

The fee structure prevents economic attacks where system operator costs exceed user fees. Without proper fee alignment, users could impose costs on operators without paying proportionally, potentially leading to reduced participation and system instability. Cardano's parameters are designed to ensure fees cover both processing and long-term storage costs.

Script Execution Fees​

When transactions execute smart contracts (for spending from script addresses, minting tokens, or validating certificates), additional fees apply based on computational resources consumed.

Execution Units​

Script costs are measured in two dimensions:

  • Memory units = peak memory used during execution (ExUnits.mem)
  • CPU steps = CPU budget consumed (ExUnits.steps)

The script fee is calculated as:

script_fee = mem_price × memory_units + step_price × cpu_steps

This fee is added to the base transaction fee. Transaction building libraries calculate execution costs automatically by simulating script execution before submission.

Collateral​

Transactions that execute scripts must provide collateral: UTXOs that are forfeited if script execution fails during Phase 2 validation.

Why collateral exists: Nodes must execute scripts to validate transactions. If a script fails, the node has already spent computational resources. Collateral compensates for this work and discourages submitting transactions that will fail.

Collateral requirements:

  • Must contain only ADA (no native tokens)
  • Must cover the potential script execution cost (typically 150-200% of expected fees)
  • Is returned if the transaction succeeds
  • Is consumed only if Phase 2 validation fails

Collateral return (CIP-40): Since the Vasil upgrade, transactions can specify a collateral return address. If collateral is consumed, any excess beyond the required amount is returned to this address rather than being entirely forfeited.

For more on two-phase validation and script execution, see the Smart Contracts Overview.

Advanced: Current Protocol Parameters

The current values of a and b are set through on-chain governance and can be queried from any Cardano node. These parameters may change over time through governance proposals to adapt to network conditions and economic factors.

To query current parameters, use:

cardano-cli query protocol-parameters

Or check via blockchain explorers that display protocol parameters.

Next Steps​