smallest-hbar-units-smart-contracts

Smallest units of HBAR in smart contracts

On the hedera main website, plus the Hedera helpdesk, the smallest unit of HBAR is the Tinybar, which is defined as 1^-8 HBAR:

• 1 Gℏ = 1,000,000,000 ℏ
• 1 Mℏ = 1,000,000 ℏ
• 1Kℏ = 1,000 ℏ
• 1 ℏ = 1 ℏ
• 1,000 mℏ = 1 ℏ
• 1,000,000 μℏ = 1 ℏ
• 100,000,000 tℏ = 1 ℏ

However, in HIP-410, the concept of a Weibar is introduced, which is defined as 1^-18 HBAR. This is even smaller than a Tinybar.

For Ethereum transactions, we introduce the concept of “WeiBars”, which are 1 to 10^-18th the value of a HBAR. This is to maximize compatibility with third party tools that expect ether units to be operated on in fractions of 10^18, also known as a Wei. Thus, 1 tinyBar is 10^10 weiBars or 10 gWei.

So within the Solidity implementation, are the units denominated in Tinybars, or Weibars?

Code

The file tinybars_demo.sol in this directory, is a smart contract with a single function named checkBalance. All it does is return the value of msg.sender.balance.

• Deploy this smart contract to any Hedera network.
• Invoke the checkBalance function from your account.
• Observe that the balance returned is 10^8 times what your wallet displays in HBAR
• Therefore the smallest unit used within Solidity smart contracts is: Weibar.
• Note that if you were to deploy this same smart contract to Ethereum, you would get a different result, where the balance returned is 10^18 times what your wallet displays in Ether

The file native_coin_units.sol in this directory, is a smart contract with several public variables that spell out the conversions more explicitly, as well as the differences between Hedera and Ethereum more explicitly.

References

• HIP-410
• What is the "full unit" of the native coin (HBAR) on Hedera?
• Hedera - HBAR
• Hedera Helpdesk - What are the official HBAR cryptocurrency denominations?