💶 Fee Estimation

Tatum makes it easy to estimate transaction fees across major blockchains:

• UTXO chains (Bitcoin, Litecoin, Bitcoin Cash): fee = feerate per byte × tx size in bytes
• EVM chains (Ethereum and EVM-compatible): fee = gasUsed × (baseFee + priorityFee)

Use this guide to understand how fees work, pick the right Tatum endpoint, and ship with confident defaults.

🔗

Jump to chain-specific guides:

• Bitcoin – How fee estimate works
• Litecoin – How fee estimate works
• Bitcoin Cash – How fee estimate works
• EVM – How gas & fee estimate works
• UTXO – Minimum relay fee
• SDK helper: JS SDK – Tatum Fee submodule

Quickly start using Fee Estimation

Option A — Get recommended fee/gas for a chain

Use when you need “fast / standard / slow” suggestions for a network.

curl --request GET \
  --url https://api.tatum.io/v3/blockchain/fee/ETH \
  --header 'x-api-key: {YOUR_API_KEY}'

Returns network-aware recommendations (e.g., baseFee, slow, medium, fast).

Option B — Estimate gas for a concrete EVM transaction

Use when you know from, to, and amount (or calldata) and want gasLimit + gasPrice.

curl --request POST \
  --url https://api.tatum.io/v4/blockchainOperations/gas \
  --header 'Content-Type: application/json' \
  --header 'x-api-key: {YOUR_API_KEY}' \
  --data '{
    "chain": "ETH",
    "from": "0x0974557990949352a20369fbe6210b3ee64....",
    "to":   "0xcdfeaf3b4a7beb3cc1fafb7ea34dc9a40b61....",
    "amount": "4.5"
  }'

Responds with

{ "gasLimit": "24126", "gasPrice": "12000000000" } // gasPrice in wei

Option C — SDK helper (multi-chain)

import { TatumSDK, Network, ApiVersion } from "@tatumio/tatum";

const tatum = await TatumSDK.init({ network: Network.ETHEREUM, version: ApiVersion.V3 });
const fee = await tatum.fee.getCurrentFee();   // slow/medium/fast + baseFee
console.log(fee.data.gasPrice.fast);

🔗

API reference:

• Get recommended fee/gas: /reference/getblockchainfee
• Estimate EVM gas for a tx: /reference/estimategas
• Estimate fee for a blockchain tx: /reference/estimatefeeblockchain

Fee models by chain

📌

For BTC/LTC/BCH, transaction size depends mainly on inputs and outputs. See:

• BTC guide | LTC guide | BCH guide

When to use which Estimation API endpoint?

• I just need the current network fees
  → GET https://api.tatum.io/v3/blockchain/fee/{chain} (slow/medium/fast)
• I know the transaction params and want gasLimit + gasPrice (EVM)
  → POST https://api.tatum.io/v4/blockchainOperations/gas
• I’m creating/broadcasting with Tatum and want a one-shot estimate
  → POST https://api.tatum.io/v3/blockchain/estimate

🧭

Tip: For smart contracts (swaps, mints, complex calls), simulate or trace for accurate gasUsed. See: EVM simulation & traces

EVM fees in 90 seconds

• Base fee (per block) + priority fee (your tip) = effective gas price.
• You set gasLimit (upper bound). You pay for gasUsed, not for gasLimit.
• Total fee (ETH) = gasUsed × (baseFee + priorityFee); units on-wire are wei (1 gwei = 10⁹ wei).

Example

• Estimated gasLimit = 24,126
• Suggested gasPrice = 12 gwei
• If gasUsed = 21,000, fee ≈ 21,000 × 12 gwei = 252,000 gwei = 0.000252 ETH.

⚠️

Too-low priority fee or gasLimit can cause "gas required exceeds allowance" or inclusion delays. Prefer fast during congestion.

UTXO fees in 90 seconds (BTC/LTC/BCH)

• Nodes/miners prioritize by feerate (sat/vByte).
• Tx size (vBytes) ≈ (inputs × 148) + (outputs × 34) + 10 (rule of thumb).
• Total fee (sats) = feerate (sat/vB) × size (vB).

Example

• Inputs: 2, Outputs: 2 → size ≈ 374 vB
• Feerate: 13.5 sat/vB → fee ≈ 374 × 13.5 = 5049 sats

📌

Also know minimum relay fee thresholds. See: UTXO – Minimum relay fee

Best practices

• Refresh often: fees are volatile; compute right before sending.
• Offer choices: expose slow / standard / fast with ETA hints in your UI.
• Guard rails: add max fee caps and sanity checks (e.g., “fee > X% of amount”).
• Simulate contracts: for complex EVM calls, run simulation or use traces.
• Handle stuck txs (UTXO): support RBF/CPFP strategies in wallets.
• Convert units correctly: EVM gasPrice is wei; display to users in gwei.

Examples of API Requests

Get recommended BTC fees (slow/standard/fast)

curl --request GET \
  --url https://api.tatum.io/v3/blockchain/fee/BTC \
  --header 'x-api-key: {YOUR_API_KEY}'

See the BTC guide for manual calculation (sat/vB × vBytes).

Estimate EVM gas for a transfer

curl --request POST \
  --url https://api.tatum.io/v4/blockchainOperations/gas \
  --header 'Content-Type: application/json' \
  --header 'x-api-key: {YOUR_API_KEY}' \
  --data '{
    "chain": "ETH",
    "from": "0x....",
    "to": "0x....",
    "amount": "0.01"
  }'

JS SDK – get current network fees

import { TatumSDK, Network, ApiVersion } from "@tatumio/tatum";
const tatum = await TatumSDK.init({ network: Network.BITCOIN, version: ApiVersion.V3 });
const fee = await tatum.fee.getCurrentFee();
console.log(fee.data.gasPrice); // slow/medium/fast/baseFee (+ unit)