Your down payment percentage affects your PMI rate and monthly payment.
A large down payment means you have more equity in the home, which reduces the lender's risk. As a result, you get a lower PMI payment. On the other hand, a small down payment increases the lender's risk, resulting in a higher PMI payment. (Loan-to-value.)
For example, PMI is cheaper when your down payment is 10% compared to 5%. And you avoid PMI altogether by putting down 20% or more.
Let's say you're buying a house for $500,000.
If you make a 10% down payment, multiply the loan amount of $450,000 by 0.3% and divide by 12 to get your monthly PMI payments of $112.50.
If you make a 5% down payment, multiply the loan amount of $475,000 by 0.45% and divide by 12 to get your monthly PMI payments of $178.13 —$65.63 more per month. Your loan amount and principal & interest payments would increase too.
Again, this is just an example. Your actual PMI payments depend on your unique situation and the lender you choose to handle your home loan.