The current value of a Bitcoin is around USD 10K. This makes it difficult for an average earning and novice investor to put in USD 10K to buy a Bitcoin. The question arises, whether we can purchase a fraction of a Bitcoin for a fraction of its value. The answer is YES. It is possible and feasible to buy less than one Bitcoin.
The unit of Bitcoin is Satoshi which is equal to 0.00000001 Bitcoin. You can buy Bitcoin in the unit of Satoshi.
When you buy Bitcoin in the Exchanges like Coinbase, Coinmama, they will simply ask you to enter the fiat currency investment amount. The inbuilt calculator of the Exchange will calculate the equivalent Bitcoin which will be credited to your wallet.
For example, if one bitcoin is worth $250, and you want to buy $125 worth of bitcoin, you’ll receive 0.50 bitcoin–assuming there are no fees.
Vice-versa, most Bitcoin brokers also let you specify the amount of bitcoin you want and will charge you the equivalent in fiat. For example, if you want to buy 0.25 bitcoin and 1 bitcoin is $300, you’ll be charged $75.
So, yes, it’s 100% possible to buy less than one bitcoin.