> ## Documentation Index
> Fetch the complete documentation index at: https://voltaire.tevm.sh/llms.txt
> Use this file to discover all available pages before exploring further.

# Blob.calculateGas

> Calculate blob gas cost for number of blobs

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  Run Blob examples in the interactive playground
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<Tabs />

## Gas Constants

```typescript theme={null}
import { Blob } from 'tevm';

console.log(Blob.GAS_PER_BLOB);        // 131,072 (2^17)
console.log(Blob.TARGET_GAS_PER_BLOCK); // 393,216 (3 blobs)
console.log(Blob.MAX_PER_TRANSACTION);  // 6 blobs

// Maximum gas per transaction
const maxGas = Blob.GAS_PER_BLOB * Blob.MAX_PER_TRANSACTION;
console.log(maxGas); // 786,432
```

## Fee Market

Blob base fee adjusts based on block usage:

```typescript theme={null}
import { Blob } from 'tevm';

// Target: 3 blobs per block
const target = Blob.TARGET_GAS_PER_BLOCK;
console.log(`Target: ${target} gas`); // 393,216

// If usage > target, fee increases
// If usage < target, fee decreases
```

### Example: Fee Adjustment

```typescript theme={null}
// Block used 2 blobs (below target)
const usedGas = Blob.calculateGas(2);
const targetGas = Blob.TARGET_GAS_PER_BLOCK;

if (usedGas < targetGas) {
  console.log('Fee will decrease next block');
}

// Block used 5 blobs (above target)
const highUsage = Blob.calculateGas(5);

if (highUsage > targetGas) {
  console.log('Fee will increase next block');
}
```

## Complete Transaction Cost

```typescript theme={null}
import { Blob } from 'tevm';

// Transaction costs
const executionGas = 21000n; // Base transaction
const executionBaseFee = 30_000_000_000n; // 30 gwei
const executionCost = executionGas * executionBaseFee;

// Blob costs
const blobCount = 2;
const blobBaseFee = 50_000_000n; // 50 gwei
const blobCost = Blob.calculateGas(blobCount, blobBaseFee);

// Total
const totalCost = executionCost + blobCost;

console.log(`Execution: ${executionCost / 10n**9n} gwei`);
console.log(`Blobs: ${blobCost / 10n**9n} gwei`);
console.log(`Total: ${totalCost / 10n**9n} gwei`);
```

## See Also

* [estimateBlobCount](./estimateBlobCount) - Estimate blobs needed
* [splitData](./splitData) - Split data into blobs
* [EIP-4844](/primitives/blob/eip4844) - Blob gas market details