Ethereum's scalability remains one of the most pressing topics in blockchain research. As network demand grows and user expectations rise, discussions around increasing the block size and gas limit have intensified. Recently, Vitalik Buterin mentioned considering a 33% increase in the gas limit to 40 million during an Ethereum Foundation Reddit AMA—sparking renewed debate.
But are we ready for larger blocks? What factors actually determine how big an Ethereum block can get? And what trade-offs must we consider to preserve decentralization while improving throughput?
This article dives into the technical and economic underpinnings of Ethereum’s block size, analyzing how variables like gas limit, calldata pricing, and EIP-4844 (Proto-Danksharding) impact scalability, security, and node requirements.
Understanding Block Size in Ethereum
Unlike Bitcoin, which enforces a fixed block size (e.g., 1MB), Ethereum uses a dynamic system measured in gas—a unit representing computational effort. Each transaction consumes gas, and every block has a gas limit, currently set at 30 million gas since the London hard fork in 2021.
However, "block size" can refer to two distinct metrics:
- Gas usage: Total gas consumed by transactions in a block.
- Byte size: Actual data volume of the block in kilobytes or megabytes.
These are related but not equivalent. For example, a block filled with zero-value calldata may consume little gas per byte (4 gas/byte) but occupy significant space. Conversely, a block with expensive operations like contract creation may hit the gas cap quickly while remaining small in bytes.
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Historical Evolution of Ethereum’s Gas Limit
The gas limit has steadily increased since Ethereum’s launch:
- 2015: Initial limit of 5,000 gas → rapidly raised to ~3 million.
- 2016: Increased to ~4.7 million; after EIP-150 (Tangerine Whistle), adjusted to 5.5 million due to DoS attack mitigations.
- 2017–2021: Gradual increases—from 6.7 million to 8 million, then 10 million in 2019, 12.5 million in 2020, and finally 15 million in April 2021.
The London hard fork (EIP-1559) introduced a new fee market mechanism with:
- A target block size of 15 million gas.
- A maximum cap of 30 million gas (2x target).
This dual-tier system allows flexibility during congestion while maintaining fee predictability through dynamic base fees.
Since then, the hard cap has remained unchanged—until now.
Are We Ready to Increase the Gas Limit?
Recent discussions, including input from core researchers like Dankrad Feist and Ansgar Diekmann, suggest that post-Dencun upgrade conditions may support a higher gas limit. However, concerns persist:
- State growth acceleration
- Node synchronization delays
- Increased risk of chain reorganizations
While large entities like Coinbase or Lido can handle larger blocks, individual validators and light clients might struggle—potentially threatening decentralization.
As hardware improves per Moore’s Law, so does our capacity to process larger blocks. But technical feasibility doesn’t override design philosophy: Ethereum prioritizes decentralized consensus over raw performance.
Calculating Maximum Block Size: The Worst-Case Scenario
To understand real-world implications, we analyze the maximum possible byte size of an Ethereum execution layer block under current constraints.
Assuming:
- Gas limit: 30 million
- Geth client enforces 128 KB max per transaction
- Fixed transaction overhead: 21,000 gas
Two extreme cases emerge:
Case 1: Zero-Value Calldata
Each byte costs 4 gas. To maximize size:
- Pack as many 128 KB transactions as possible.
- Result: ~55 transactions → ~6.88 MB raw size.
- After Snappy compression (efficient for repetitive zeros): ~0.32 MB.
Case 2: Non-Zero Calldata
Each byte costs 16 gas. Higher cost limits data volume:
- Only ~14–15 full-sized transactions fit.
- Raw size: ~1.75–1.875 MB.
- Compression less effective → final size: ~1.77 MB.
Thus, the current practical upper bound for compressed block size is approximately 1.77 MB.
Key Factors Influencing Block Size
1. Gas Limit
Higher gas limits directly enable larger blocks. The relationship is roughly linear: doubling the gas limit allows nearly double the data (assuming same calldata cost).
At 40 million gas, worst-case block size could reach ~2.36 MB—before blobs.
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2. Calldata Pricing
Pricing dictates how much data fits within the gas budget.
- At 16 gas/byte (current): ~1.77 MB max.
- At 8 gas/byte: double the data → ~3.5 MB.
- At 32 gas/byte: half the data → ~0.88 MB.
This shows why proposals like EIP-4488 (reducing calldata cost with daily caps) are debated—they boost scalability but increase historical data burden.
3. Client-Side Transaction Limits
Geth’s 128 KB per transaction cap indirectly reduces efficiency:
- More transactions = more fixed 21k gas fees.
- Up to ~0.07 MB loss in potential block size due to overhead.
While this only affects broadcasting (not consensus), it still shapes real-world behavior.
EIP-4844 and Multi-Dimensional Fee Markets
EIP-4844 (Proto-Danksharding) introduces blobs—temporary data containers holding up to ~125 KB each.
Key features:
- Separate fee market from main gas (multi-dimensional pricing).
- Target: 3 blobs/block; Max: 6 blobs/block.
- Blob data is pruned after ~18 days, reducing long-term storage pressure.
Impact on average block size:
- Current avg (compressed): ~125 KB.
- With 3 blobs: +375 KB → total ~500 KB (4x increase).
- With 6 blobs: +750 KB → total ~875 KB (7x increase).
Worst-case execution layer blocks grow from ~1.77 MB to ~2.5 MB when including blob payloads.
This shift enables cheaper rollup transactions without bloating state—balancing scalability and decentralization.
Frequently Asked Questions (FAQ)
Q: What is the current Ethereum gas limit?
A: The maximum gas limit is 30 million per block, set during the London hard fork in 2021.
Q: How does increasing the gas limit affect decentralization?
A: Larger blocks require more bandwidth and storage, potentially excluding smaller validators and weakening network decentralization.
Q: What is the difference between calldata and blob data?
A: Calldata is permanent and processed by EVM; blob data is temporary, cheaper, and used mainly by rollups for data availability.
Q: Why not just make blocks bigger like Solana?
A: Ethereum prioritizes running on consumer hardware. Larger blocks favor centralized infrastructure, conflicting with core values.
Q: How does EIP-1559 improve fee predictability?
A: It introduces a dynamically adjusted base fee that rises during congestion and falls during low demand, smoothing transaction costs.
Q: Can blob data be compressed?
A: Blobs use efficient encoding (KZG commitments) but aren’t compressed like execution payloads; they’re designed for short-term storage.
Conclusion: Balancing Scalability and Decentralization
Increasing Ethereum’s gas limit to 40 million is technically feasible—but comes with trade-offs. Larger blocks improve throughput but strain node operators, especially independent stakers.
True scalability lies not just in bigger blocks, but in smarter architecture:
- Multi-dimensional fee markets (EIP-1559 + EIP-4844)
- Data sharding roadmap
- Efficient compression and pruning
As Ethereum evolves, decisions must be guided by data—not hype. The goal isn’t to outperform centralized chains in raw speed, but to scale securely while preserving open participation.
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Ultimately, building a system as robust as Facebook is easy—it's keeping it decentralized that's hard. And that’s what makes Ethereum unique.