cardano-protocol-params

When to use

•Fetching fresh protocol parameters
•Understanding fee calculation inputs
•Debugging min-UTxO or execution budget issues
•Comparing params across networks

Operating rules (must follow)

•Always fetch fresh params for the target network
•Never assume mainnet params apply to testnets
•Keep pparams.json with tx artifacts for reproducibility

Key parameters explained

Fee calculation

code

minFeeA: 44           # lovelace per byte
minFeeB: 155381       # base fee in lovelace

Formula: fee = minFeeA * txSize + minFeeB

Min UTxO

code

coinsPerUTxOByte: 4310   # lovelace per byte of UTxO

Minimum ADA required = size of UTxO (including datum) × coinsPerUTxOByte

Execution units (Plutus)

code

maxTxExecutionUnits:
  steps: 10000000000     # CPU budget
  memory: 10000000       # Memory budget
executionUnitPrices:
  priceSteps: 0.0000721  # lovelace per step
  priceMemory: 0.0577    # lovelace per memory unit

Reference scripts

code

minFeeRefScriptCostPerByte: 15  # Cost for using reference scripts

Workflow

Fetch parameters

bash

# Preprod
cardano-cli conway query protocol-parameters \
  --testnet-magic 1 \
  --out-file pparams-preprod.json

# Mainnet
cardano-cli conway query protocol-parameters \
  --mainnet \
  --out-file pparams-mainnet.json

Extract key values

bash

# Using jq
cat pparams.json | jq '{
  minFeeA: .txFeePerByte,
  minFeeB: .txFeeFixed,
  coinsPerUTxOByte: .utxoCostPerByte,
  maxTxSize: .maxTxSize,
  maxValSize: .maxValueSize
}'

Calculate min-UTxO for output

bash

# Approximate: base ~160 bytes + datum size
# For simple ADA-only output: ~1 ADA minimum
# For output with tokens: varies by token count/names

Examples

Example: Debug "UTxO too small" error

Problem: Transaction fails with min-UTxO error

Response:

bash

# 1. Fetch current params
cardano-cli conway query protocol-parameters \
  --testnet-magic 1 \
  --out-file pparams.json

# 2. Check coinsPerUTxOByte
cat pparams.json | jq .utxoCostPerByte
# Result: 4310

# 3. Estimate min-UTxO for your output
# Simple ADA output: ~160 bytes × 4310 = ~690,000 lovelace
# With inline datum: add datum size × 4310
# With tokens: add ~30 bytes per token

# 4. Solution: increase output amount above minimum

Example: Estimate script execution cost

Problem: Need to budget for Plutus script

Response:

bash

# 1. Get execution prices
cat pparams.json | jq '{
  priceSteps: .executionUnitPrices.priceSteps,
  priceMemory: .executionUnitPrices.priceMemory
}'

# 2. If script uses 1M steps and 100K memory:
# Cost = (1000000 × 0.0000721) + (100000 × 0.0577)
# Cost = 72.1 + 5770 = 5842.1 lovelace (~0.006 ADA)

# 3. Add to base tx fee for total

Network magic reference

code

Mainnet:  (no flag, use --mainnet)
Preprod:  --testnet-magic 1
Preview:  --testnet-magic 2

Safety / key handling

•Protocol params are public, no secrets involved
•Always verify you're querying the intended network
•Store pparams with tx artifacts for debugging

References

•shared/PRINCIPLES.md
•Cardano Protocol Parameters