Gas Costs for Solidity Built-in Functions

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Gas Costs for Solidity Built-in Functions

Operation	Gas Cost	Notes
Simple Arithmetic
+, -, *, /, %	3–5 gas	Basic integer math. Division is more expensive.
** (exponentiation)	10–100+ gas	Cost scales with exponent size.
++, --	3–5 gas	Increment/decrement.
Storage Operations
SSTORE (write new value)	20,000–22,100 gas	22,100 for new storage slot, 20,000 for updating existing non-zero value.
SSTORE (set to zero)	500–5,000 gas	Gas refund may apply.
SLOAD (read storage)	2,100 gas	Reading from storage.
Memory Operations
MLOAD (read memory)	3 gas
MSTORE (write memory)	3–6 gas
Ether Transfers
address.transfer()	2,300 gas stipend	Fixed gas, reverts on failure.
address.send()	2,300 gas stipend	Returns bool, does not revert.
address.call{value: x}()	All remaining gas	Flexible but risky (reentrancy).
Hashing & Cryptography
keccak256()	30–60 gas	Cost depends on input size.
sha256()	60+ gas	More expensive than keccak256.
Contract Operations
new Contract()	32,000+ gas	Base cost + deployment bytecode execution.
selfdestruct(address)	5,000 gas	Refunds may apply.
Logging (Events)
emit Event()	375–2,000+ gas	Base cost + 375 gas per topic + 8 gas per byte of data.
Control Flow
require() / revert()	10–30 gas	Early termination with message costs more.
assert()	10–30 gas	Similar to require but for internal errors.
Function Calls
External call (contract.func())	700+ gas	Base cost + function execution.
Internal call (this.func())	100–300 gas	Cheaper than external calls.

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Key Notes

1. Gas Costs Are Approximate:
   • Actual costs depend on compiler optimizations, EVM upgrades, and context (e.g., cold vs. warm storage access).
2. Storage vs. Memory:
   • Storage (SSTORE/SLOAD) is 1,000x+ more expensive than memory (MSTORE/MLOAD).
3. Ether Transfers:
   • transfer and send limit gas to 2,300 (preventing reentrancy but risky for contracts).
   • call forwards all gas (use with checks-effects-interactions).
4. Refunds:
   • Setting storage to zero (SSTORE to 0) may refund up to 4,800 gas.

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Example Gas Calculation

function example() public {
    uint a = 1;          // ~3 gas (memory write)
    a += 1;              // ~3 gas (arithmetic)
    emit Log(a);         // ~500 gas (1 topic + data)
    require(a > 0, "!"); // ~25 gas
}

Total: ~531 gas (excluding function call overhead).

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For precise gas estimation, use:

• Hardhat: hardhat-gas-reporter plugin.
• Remix: Gas meter in the debugger.
• Etherscan: Check gas used in confirmed transactions.