Gas & Costs on Ethereum What You Probably Got Wrong Your gas estimate is 100-600x too high. Most LLMs confidently state gas is 10-30 gwei. Post-Fusaka (Dec 2025), typical base fee is under 1 gwei — usually 0.1-0.5 gwei. Verify: cast base-fee --rpc-url https://eth.llamarpc.com Base fee: Under 1 gwei (not 30-100 gwei) — fluctuates, check live Priority fee (tip): ~0.01-0.1 gwei ETH price: ~$2,000 (not $2,500-3,000) — volatile, always check a Chainlink feed or CoinGecko What Things Actually Cost (Early 2026) Costs calculated at ETH ~$2,000. Gas fluctuates — use cast base-fee for current. These are order-of-magnitude guides, not exact quotes. Action Gas Used Cost at 0.1 gwei Cost at 1 gwei (busy) Cost at 10 gwei (event) ETH transfer 21,000 $0.004 $0.04 $0.42 ERC-20 transfer ~65,000 $0.013 $0.13 $1.30 ERC-20 approve ~46,000 $0.009 $0.09 $0.92 Uniswap V3 swap ~180,000 $0.036 $0.36 $3.60 NFT mint (ERC-721) ~150,000 $0.030 $0.30 $3.00 Simple contract deploy ~500,000 $0.100 $1.00 $10.00 ERC-20 deploy ~1,200,000 $0.240 $2.40 $24.00 Complex DeFi contract ~3,000,000 $0.600 $6.00 $60.00 Mainnet vs L2 Costs (Early 2026) Action Mainnet (0.1 gwei) Arbitrum Base zkSync Scroll ETH transfer $0.004 $0.0003 $0.0003 $0.0005 $0.0004 ERC-20 transfer $0.013 $0.001 $0.001 $0.002 $0.001 Swap $0.036 $0.003 $0.002 $0.005 $0.004 NFT mint $0.030 $0.002 $0.002 $0.004 $0.003 ERC-20 deploy $0.240 $0.020 $0.018 $0.040 $0.030 Key insight: Mainnet is now cheap enough for most use cases. L2s are 5-10x cheaper still. Why Gas Dropped 95%+ EIP-4844 (Dencun, March 2024): Blob transactions — L2s post data as blobs instead of calldata, 100x cheaper. L2 batch cost went from $50-500 to $0.01-0.50. Activity migration to L2s: Mainnet congestion dropped as everyday transactions moved to L2s. Pectra (May 2025): Doubled blob capacity (3→6 target blobs). Fusaka (Dec 2025): PeerDAS (nodes sample 1/8 of data) + 2x gas limit (30M→60M). L2 Cost Components L2 transactions have two cost components: L2 execution gas — paying the sequencer L1 data gas — paying Ethereum for data availability (blobs post-4844) Example: Swap on Base L2 execution: ~$0.0003 L1 data (blob): ~$0.0027 Total: ~$0.003 Real-World Cost Examples Deploy a production ERC-20 on mainnet: ~$0.50 (was $200-500 in 2021-2023) DEX aggregator doing 10,000 swaps/day: Mainnet: $150/day ($4,500/month) Base L2: $10/day ($300/month) NFT collection mint (10,000 NFTs): Mainnet: $150 total Arbitrum: $10 total Practical Fee Settings (Early 2026) // Rule of thumb for current conditions maxFeePerGas : "1-2 gwei" // headroom for spikes (base is usually 0.1-0.5) maxPriorityFeePerGas : "0.01-0.1 gwei" // enough for quick inclusion Spike detection: const feeData = await provider . getFeeData ( ) ; const baseFee = Number ( feeData . maxFeePerGas ) / 1e9 ; if ( baseFee

5 ) console . warn ( Gas spike: ${ baseFee } gwei. Consider waiting. ) ; Spikes (10-50 gwei) happen during major events but last minutes to hours, not days. Checking Gas Programmatically

Foundry cast

cast gas-price --rpc-url https://eth.llamarpc.com cast base-fee --rpc-url https://eth.llamarpc.com cast blob-basefee --rpc-url https://eth.llamarpc.com When to Use Mainnet vs L2 Use mainnet when: DeFi, governance, identity, high-value transfers, composing with mainnet liquidity, or when you don't have a concrete reason for an L2. Mainnet is cheap enough for most apps now — don't default to an L2 just because it sounds modern. Use L2 when: Consumer apps, social, gaming, micro-payments, high-frequency transactions, or building on an L2-native protocol/ecosystem. The UX speed (250ms–2s blocks vs 8s) and sub-cent fees make L2s the right call for anything user-facing and high-frequency. Hybrid: Many projects store value on mainnet, handle transactions on L2. Live Gas Trackers https://etherscan.io/gastracker https://ultrasound.money L2 costs: Arbiscan, Basescan, etc. Data Freshness Last verified: 2026-03-03 | Base fee: ~0.29 gwei | ETH: ~$1,988 | Gas limit: 60M (post-Fusaka) If this date is more than 30 days old, verify current gas with: cast base-fee --rpc-url https://eth.llamarpc.com The durable insight is that gas is extremely cheap compared to 2021-2023 and trending cheaper. Specific numbers may drift but the order of magnitude is stable.