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Web3 & DApp Development Fundamentals · レッスン

Gasコストモデル

Gasが必要な処理

「Gasコストモデル」はCoddyKit上の無料Web3 & DApp Development Fundamentalsレッスンです。 これはレッスン1/4です。 下記で完全なレッスンを無料で読むことができます。その後、ブラウザ内の組み込みコードエディタと24時間対応のAIチューターでハンズオン演習できます。 これはWeb3 & DApp Development Fundamentals学習パスの一部であり、ウェブとCoddyKitアプリ全体で進捗が同期されます。 Web3 & DApp Development Fundamentalsコースには全4レッスンが含まれています。

このレッスンの一部はまだ翻訳されておらず、英語で表示されています。

Why Gas Exists

Every operation on the Ethereum Virtual Machine (EVM) costs gas. Gas is a unit that measures the computational work required to execute a transaction.

Gas exists to:

  • Pay validators for the resources they spend
  • Prevent infinite loops and denial-of-service attacks
  • Price scarce on-chain resources fairly

The total fee you pay equals gasUsed * gasPrice, denominated in wei.

Gas, Gas Price, and Gas Limit

Three numbers matter for every transaction:

  • gasUsed — how much computation actually happened
  • gasPrice (or maxFeePerGas under EIP-1559) — how much you pay per unit
  • gasLimit — the maximum gas you allow before the transaction reverts

If execution exceeds the gas limit, the transaction reverts with an out of gas error, but you still pay for the gas consumed.

// Fee calculation
// totalFee = gasUsed * effectiveGasPrice
// Example: 50000 gas * 20 gwei = 1,000,000 gwei = 0.001 ETH

Opcode Costs

Each EVM opcode has a fixed gas cost defined in the Ethereum protocol. Cheap arithmetic costs very little, while storage and external calls cost a lot.

  • ADD, SUB — 3 gas
  • MUL — 5 gas
  • SLOAD (read storage) — 2100 gas cold, 100 warm
  • SSTORE (write storage) — up to 22100 gas

Storage dominates the cost of most contracts.

The Cost of Storage

Persistent storage is the single most expensive resource on the EVM. Writing a storage slot from zero to non-zero costs 20000 gas; updating a non-zero slot costs 5000 gas.

Reading is cheaper than writing but still significant. This is why the golden rule of gas optimization is: touch storage as rarely as possible.

contract Counter {
    uint256 public count; // each increment writes a storage slot

    function increment() external {
        count += 1; // 1 SLOAD + 1 SSTORE
    }
}

Memory vs Storage vs Calldata

The EVM has three data locations, each with a different cost profile:

  • storage — persistent, most expensive
  • memory — temporary per-call, cheap but grows quadratically
  • calldata — read-only input data, cheapest for function arguments

Using calldata instead of memory for external function parameters avoids an unnecessary copy.

function sum(uint256[] calldata nums) external pure returns (uint256 total) {
    for (uint256 i = 0; i < nums.length; i++) {
        total += nums[i];
    }
}

Intrinsic Gas

Before any code runs, every transaction pays a base cost called intrinsic gas:

  • 21000 gas for a base transaction
  • 16 gas per non-zero calldata byte
  • 4 gas per zero calldata byte

This means even an empty transfer costs 21000 gas, and larger calldata payloads make transactions more expensive before execution even begins.

Cold vs Warm Access

Since EIP-2929, the first access to an account or storage slot in a transaction is cold and expensive; subsequent accesses are warm and cheap.

  • Cold SLOAD: 2100 gas
  • Warm SLOAD: 100 gas
  • Cold account access: 2600 gas

Caching a storage value in a local variable converts repeated cold reads into a single read plus cheap memory access.

uint256 cached = count; // one SLOAD
for (uint256 i = 0; i < cached; i++) {
    // use cached instead of re-reading count
}

Refunds

The EVM grants a partial gas refund when you clear storage, setting a non-zero slot back to zero (via SSTORE or SELFDESTRUCT historically).

Refunds are capped at one fifth of the transaction gas used (EIP-3529). Patterns like deleting array elements or zeroing balances can recover some gas, but you should never rely on refunds as a primary optimization.

function clear(uint256 key) external {
    delete data[key]; // zeroing a slot triggers a refund
}

EIP-1559 Fee Market

EIP-1559 split the gas price into two parts:

  • base fee — burned, adjusts automatically per block based on demand
  • priority fee (tip) — paid to the validator

Users set maxFeePerGas and maxPriorityFeePerGas. The effective price never exceeds the max, and unused amounts are refunded. This makes fees more predictable.

Deployment vs Runtime Gas

Contracts have two distinct gas profiles:

  • Deployment gas — paid once, proportional to bytecode size (200 gas per byte stored)
  • Runtime gas — paid on every call to the deployed contract

Sometimes you trade a larger, more expensive deployment for cheaper runtime, or vice versa. Optimize for the dimension that matters most to your use case.

The Optimization Mindset

Effective gas optimization follows a hierarchy:

  • Avoid storage writes (biggest wins)
  • Minimize cold accesses by caching
  • Use calldata over memory
  • Reduce calldata size
  • Micro-optimize opcodes last

Always measure before and after. Premature micro-optimization often hurts readability for negligible gain.

Quick Check

Which operation is typically the most expensive in an EVM contract?

Recap

You now understand the EVM gas cost model:

  • Fees equal gasUsed * gasPrice, bounded by a gas limit
  • Storage writes dominate cost; arithmetic is cheap
  • Cold accesses cost more than warm ones
  • Intrinsic gas (21000 + calldata bytes) is paid before execution
  • EIP-1559 splits fees into a burned base fee and a validator tip

Next we apply this knowledge to optimize contract storage layout.

よくある質問

「Gasコストモデル」レッスンは無料ですか？

はい。「Gasコストモデル」の完全なテキストはこのウェブで無料で読めます。インタラクティブに演習し（組み込みコードエディタと24時間対応のAIチューター）、Web3 & DApp Development Fundamentalsコースの残りをアンロックするには、CoddyKit PROにアップグレードしてください。 Web3 & DApp Development Fundamentalsコースには全4レッスンが含まれています。

「Gasコストモデル」で何を学びますか？

Gasが必要な処理 ブラウザで直接実行するハンズオンコードでWeb3 & DApp Development Fundamentalsを演習し、24時間対応のAIチューターがレッスンを進める中での質問に答えます。

Web3 & DApp Development Fundamentalsを始めるのに経験は必要ですか？

事前経験は必要ありません。CoddyKitのWeb3 & DApp Development Fundamentalsは初級者から上級者向けに構成されているため、ここから始めるか最初から始めて、自分のペースで進むことができます。 これはレッスン1/4です。

「Gasコストモデル」レッスンにはどのくらい時間がかかりますか？

ほとんどのCoddyKitレッスンは約5～10分かかります。各レッスンはコンパクトでインタラクティブなので、着実に進歩し、ウェブとアプリ全体で正確に前回の場所から再開できます。

このWeb3 & DApp Development Fundamentalsレッスンでコードを書いて実行できますか？

はい。すべてのWeb3 & DApp Development Fundamentalsレッスンに組み込みコードエディタが含まれているため、ブラウザでリアルコードを書いて実行し、即座のAIフィードバックを取得できます。ローカル設定は不要です。

このコースのすべてのレッスン

  1. Gasコストモデル
  2. ストレージ最適化
  3. ループとCalldataのテクニック
  4. Gasの測定
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