This gets right to the heart of the precision difference between Ethereum and Bitcoin, and how a system like Bitlayer reconciles the two.

⚖️ ETH vs BTC Precision

Unit	Smallest Subdivision	Decimal Places
ETH	1 wei = 10⁻¹⁸ ETH	18 decimals
BTC	1 satoshi = 10⁻⁸ BTC	8 decimals

So 1 wei (0.000000000000000001 ETH) is 10⁻¹⁰ smaller than 1 satoshi, the smallest BTC unit.

So… how is 1 wei expressed in BTC?

It can’t be expressed in real BTC — only virtually.

Because Bitcoin itself does not support more than 8 decimal places, 1 wei must be handled by Bitlayer’s internal accounting system, not on Bitcoin L1.

How Bitlayer Handles It

Internal Ledger Precision

Bitlayer can define its own internal token format (e.g. bBTC) to allow more than 8 decimals, like 18 decimals (just like ETH).

So, 1 wei = 0.000000000000000001 bBTC is valid inside Bitlayer’s Layer 2, even if it’s not valid on Bitcoin L1.

Gas Accounting

When a contract on Bitlayer consumes 21,000 gas at 1 wei gas price:

21,000 wei = 0.000000000000021 bBTC

This is debited from the user’s Bitlayer wallet balance, not the actual Bitcoin blockchain.

Rounding at Exit

When you withdraw BTC back to L1, Bitlayer rounds down to the nearest satoshi.

Any remaining microdust (fractions below 1 satoshi) is usually:

• Left behind (not withdrawable)
• Accumulated for future use
• Or “burned” depending on protocol design

Summary

Concept	ETH (L1)	BTC (L1)	Bitlayer (L2)
Smallest unit	1 wei (10⁻¹⁸)	1 satoshi (10⁻⁸)	1 “wei” equivalent in bBTC with 18 decimals
Can 1 wei exist on BTC L1?	❌ No	✅ But only ≥1 satoshi	✅ Yes, internally on Bitlayer only
How it works	Native	Native	Virtual balance tracked in high precision

Real-World Analogy:

Think of Bitlayer’s bBTC like a store credit system:

• It mirrors BTC for user spending inside the platform
• But it can track smaller fractions than BTC allows
• Only when you exit the store (withdraw BTC) do you round back to full satoshis