# Why Do Web3 Applications Need BigNumber?

**Published by:** [@0xhenrydev](https://paragraph.com/@0xhenrydev/)
**Published on:** 2025-05-22
**URL:** https://paragraph.com/@0xhenrydev/why-do-web3-applications-need-bignumber

## Content

How Should We Handle Precision Issues in JavaScript?🧠 Background: JavaScript Precision LimitationJavaScript's native Number type is a 64-bit floating point number (IEEE 754). This limits its integer precision to 2^53 - 1, or about 9e15. Beyond that, numbers get rounded and lose accuracy.console.log(Number.MAX_SAFE_INTEGER); // 9007199254740991 console.log(9007199254740991 + 1); // 9007199254740992 ✅ console.log(9007199254740991 + 2); // 9007199254740992 ❌ precision loss 💰 Why This Is a Problem in Web3Ethereum (and other EVM chains) use wei as the smallest unit of ETH.1 ETH = 10^18 wei → sending just 1 ETH involves manipulating a big integer, far beyond JS safe integer range.Smart contracts return values in wei, making it unsafe to use regular Number for balances, gas, token supply, etc.✅ Solution: Use BigNumber or BigIntTo safely handle large numbers in Web3 apps, you must use arbitrary-precision number types, like:ethers.BigNumber (from ethers.js)BigNumber.js (arbitrary precision lib)Native BigInt (ES2020)web3.utils.BN (if using web3.js)Example (using ethers.js):import { parseEther, formatEther } from 'ethers'; const amountInWei = parseEther('1.0'); // returns BigNumber of 10^18 console.log(amountInWei.toString()); // '1000000000000000000' const readable = formatEther(amountInWei); // back to human-readable ETH console.log(readable); // '1.0' 🧪 Common Pitfall: Converting BigNumber to JS NumberAvoid this unless you're 100% sure the value is within the safe range:const unsafe = BigNumber.from("1000000000000000000"); console.log(unsafe.toNumber()); // May throw or round incorrectly if too large Instead, use:console.log(unsafe.toString()); // Safe 💡 When to Use BigInt?If you don’t need compatibility with libraries like ethers.js, and you’re just doing arithmetic:const a = BigInt("1000000000000000000"); const b = BigInt("3000000000000000000"); const c = a + b; console.log(c.toString()); // "4000000000000000000" But be careful: BigInt ≠ Number, and you can’t mix them.🧩 Summary: Why BigNumber is Essential in Web3ReasonExplanation✅ PrecisionJS Number can't represent large wei values accurately💡 CompatibilityWeb3 libraries return balances and values as BigNumber🔒 SafetyPrevent silent rounding bugs in balances, gas, etc.🛠️ ToolsUse parseEther, formatUnits, BigNumber.from, etc.

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