# Ethereum Blob Fees and Blobs per Block vs Target

> Track Ethereum blob fees: the blob base fee, blobs per block against the target and maximum, cost per blob and blob space bought by each rollup, block by block.

Markdown copy of https://voltfincrypto.com/apps/ethereum-blob-fees

**Question:** How many blobs are used per block versus the target, and what does a blob cost right now?

- Kind: Dashboard in Voltfin Vantage
- Topic: [Layer 2s](https://voltfincrypto.com/topics/layer-2)
- Chains: Ethereum
- Status: Planned. The data is not published yet, so this page states no figure; each figure will open its receipt when it is.

Blobs are the data space rollups buy on Ethereum to publish their batches. Each block can carry up to a maximum number of blobs, and the blob base fee rises when blocks carry more than the target and falls when they carry fewer. This dashboard reads both from every block header, so the price and the usage are exact.

Since the Fusaka upgrade, blob capacity can be raised through small blob-parameter-only forks, and the blob base fee is held up by a reserve price tied to the execution base fee. The dashboard marks each fork on its charts, with the target and maximum in force at every block.

Use it to see whether blob space is scarce, what a rollup pays to post a blob and which rollups use the most. Every figure is pinned to its block, with the header fields it came from.

## Blueprint

### Now

The latest blob price and how full recent blocks were.

- **Blob base fee** (gwei): The blob base fee of the latest finalized block, computed from its excess_blob_gas.
- **Cost of one blob** (USD): The blob base fee times the blob gas in one blob at the latest finalized block, in ETH and USD.
- **Blobs in the latest block** (blobs): Blobs carried by the latest finalized block, against the target and the maximum in force.
- **Blobs per block, last hour** (blobs): The average number of blobs per block over the last hour, against the target.
- **Blobs per block, recent blocks** (blobs): Blobs in each recent block drawn against the target and maximum lines, so stretches above target show where the fee rises.

### History

Blob usage and price by day, by rollup and across forks.

- **Blobs per day** (blobs): Blobs posted on the latest complete day, from every block of the day.
- **Blocks above target** (%): The share of the latest complete day's blocks that carried more blobs than the target.
- **Blob base fee by day** (gwei): The median and the highest blob base fee of each day, with each fork marked.
- **Blobs by rollup by day** (blobs): Blobs posted each day, stacked by the rollup that posted them, against the day's target capacity.

Filters: Period (Last day, week, month or year).

## How it will be measured

- Blobs per block are blob_gas_used from each header divided by the blob gas in one blob; the target and maximum come from the fork schedule in force at that block.
- The blob base fee is computed from the header's excess_blob_gas with the active fork's update fraction, and checked against blobGasPrice in the receipts of type-3 transactions in the same block.
- Since Fusaka, EIP-7918 stops the blob base fee from falling while it sits below a reserve price tied to base_fee_per_gas; the dashboard marks the blocks where that rule applied.
- Blob transactions are attributed to rollups by their sender (the batcher) and destination (the batch inbox), from a maintained registry; unknown senders are shown as other.
- The cost of one blob is the blob base fee times the blob gas in one blob, converted to USD with the Chainlink ETH/USD feed at the same block.

## Data it needs

- `gas_blocks` (to build): Base fee, priority fee percentiles, gas used and gas limit for each block on fee-market chains, for a near-live gas tracker.
- `blob_usage_daily` (to build): EIP-4844 blobs posted per day, blob gas used, blob base fee, and the rollup that posted them.
- `native_prices_daily` (to build): Reference prices of major assets read from on-chain oracle feeds (Chainlink latestRoundData) at each day's last block, with each round's update time.
- Source: blob_gas_used and excess_blob_gas from every Ethereum block header
- Source: Type-3 transactions: blob_versioned_hashes counts, and blobGasPrice and blobGasUsed from their receipts
- Source: The fork schedule: activation epochs with each fork's blob target, maximum and update fraction
- Source: A registry of rollup batcher and batch inbox addresses
- Source: Chainlink ETH/USD at the same block for USD values

## Questions

### What is a blob on Ethereum?

A blob is a large, fixed-size piece of data attached to a type-3 transaction, introduced by EIP-4844. Rollups use blobs to publish their batches. Blobs have their own fee market, and consensus nodes keep blob data for a limited period rather than forever, which is why blob space usually costs far less than calldata.

### How is the blob base fee set?

Like the execution base fee, it follows demand: each block that carries more blobs than the target raises it, and each that carries fewer lowers it, through a running excess_blob_gas counter in the block header. It is paid in ETH and burned.

### What are the blob target and maximum?

The target is the number of blobs per block that the fee market aims for; the maximum is the most a block may carry. Both are protocol parameters, and since Fusaka they can be raised by blob-parameter-only forks without a full network upgrade.

### What did PeerDAS change?

PeerDAS (EIP-7594) lets nodes confirm that blob data is available by sampling pieces of it instead of downloading every blob. That lowers the bandwidth each node needs, which is what allows the blob target and maximum to rise.

### Why are blob fees sometimes close to zero?

When blocks carry fewer blobs than the target for a long stretch, the blob base fee falls toward its minimum. Since Fusaka the reserve price stops it from sinking far below a level tied to the execution base fee, so rollups still pay something for the data they post.

## Glossary

- **Blob**: A fixed-size data attachment to a type-3 transaction, kept by consensus nodes for a limited time and used by rollups to publish batches.
- **Blob gas**: The separate unit blobs are priced in, with its own base fee, apart from the gas that pays for execution.
- **Excess blob gas**: A block header field that tracks blob usage above the target over time; the blob base fee is computed from it.
- **BPO fork**: A blob-parameter-only fork: a small network upgrade that changes only the blob target, the maximum and the fee update fraction.

## Related apps

- [Fusaka Upgrade Impact: Blobs, L2 Fees and Spam](https://voltfincrypto.com/apps/fusaka-upgrade-impact)
- [L2 Profitability: Fees Earned vs Costs Paid to Ethereum](https://voltfincrypto.com/apps/l2-profitability)
- [Ethereum Gas Tracker](https://voltfincrypto.com/apps/ethereum-gas-tracker)
- [Next Ethereum Upgrade: Glamsterdam Status and Fork History](https://voltfincrypto.com/apps/next-ethereum-upgrade)
- [Ethereum L2 Fees Compared: Cost per Transaction](https://voltfincrypto.com/apps/ethereum-l2-fees)
- [Ethereum TPS: Mainnet and Layer 2 Transactions per Second](https://voltfincrypto.com/apps/ethereum-tps)

Build it in Voltfin Studio: https://app.voltfincrypto.com/signup?next=%2F