As a Solidity developer, it’s important for you to understand how to use Solidity units correctly.

They are equivalent to real-world currency and time units, such as pennies, pounds, dollars, or seconds, minutes, and hours. By learning how to use them, you will ensure that your smart contracts execute properly and provide secure, transparent, and reliable operations on the blockchain.

By the end of this step, you will be able to use Solidity units to accurately represent and manipulate values of tokens, as well as durations of time within a contract.

Currency units

Decorative: A hand holding an Ethereum coin

In Solidity, there are different types of units available. The following are units used to indicate the denomination of a numerical value. They are used to indicate the level of precision of a value and to make it easier for developers and users to understand the meaning of a value (see Figure 1 below):

Pyramid-shaped representation of Ether units, ranging from the smallest denomination, wei, at the top to the largest denomination, ether, at the bottom. 1 wei = 1 1 gwei = one billion wei 1 szabo = one million gwei 1 finney = one thousand szabo 1 ether = one thousand finney

Figure 1: A pyramid-shaped representation of Ether units, ranging from the smallest denomination of Ether at the top (wei) to the largest denomination of Ether at the bottom (ether).

For example, if you want to represent 1 ether, you can write it as 1,000,000,000,000,000,000 wei or 1,000,000,000,000,000,000,000 szabo.

Time units

Decorative: A clock at 3pm.

Time units are used to indicate the duration of a time period. They are used to make it easier for developers and users to understand the meaning of a time value. The following are the time units available in Solidity and a time period they represent (see Figure 2 below):

1 = 1 second, 1 minute = 60 seconds, 1 hour = 60 minutes, 1 day = 24 hours, 1 week = 7 days, 1 year = 365 days

Figure 2: Graphic illustrating the conversion of time units in Solidity.

For example, if you want to represent a duration of 1 hour, you can write it as 60 minutes or 3600 seconds.

Decorative: Reflect banner

Take a moment to reflect on what you’ve learnt in this step.

Consider the various unit types available in Solidity, such as wei, ether, seconds, minutes, and days. How might the selection of these unit types impact the accuracy, readability, and usability of a smart contract? Try to come up with a few examples to support your thoughts.

In the next step, you'll find a sample answer waiting for you.

When you’re ready, select Next to continue.

Units