gas

What this skill does

# 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](https://data.chain.link/feeds/ethereum/mainnet/eth-usd) 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%+

1. **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.
2. **Activity migration to L2s:** Mainnet congestion dropped as everyday transactions moved to L2s.
3. **Pectra (May 2025):** Doubled blob capacity (3→6 target blobs).
4. **Fusaka (Dec 2025):** PeerDAS (nodes sample 1/8 of data) + 2x gas limit (30M→60M).

## L2 Cost Components

L2 transactions have two cost components:
1. **L2 execution gas** — paying the sequencer
2. **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)

```javascript
// 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:**
```javascript
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

```bash
# Foundry cast
cast gas-price --rpc-url https://eth.llamarpc.com
cast base-fee --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:** 2026-03-17 | Base fee: ~0.05 gwei | ETH: ~$2,329 | Gas limit: 60M (post-Fusaka)

If this date is more than 30 days old, verify current gas with:
```bash
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.

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