There’s no hard and fast amount of available credit required to rent a car. It depends on the per-day cost of the rental and the number of days you need it. Typically, the rental agency puts a hold on your credit card for at least the amount of the rental and a little extra on top of that, in case there's a problem.
Gimme Some Wheels
Many rental car companies require that you be at least 21 and have a credit card in your name to rent a car. Some may go down to age 18 and take cash or a debit card. Companies usually prefer credit cards with a healthy available balance – the amount of your credit limit minus your current balance. If you have a credit card with a $1,000 limit and a $200 current balance, your available balance is $800, which should be enough – most of the time.
Rental car companies require a certain dollar amount on your available balance in case you exceed your mileage, keep the car longer than promised or cause damages. It's easier for the company to charge your card for extra expenses than to spend time and money collecting the additional charges after the fact. Polices vary from company to company, so ask for the amounts when making a reservation.
Expect to have at least the estimated amount of your rental and an extra $200 put on your card for incidentals. Companies almost always put a hold on a debit card, but may not place one on your credit card depending on your available balance and their policies. A hold or block means you can't use the funds until the car is returned and paid for. If your estimated cost of renting the car is $100 for two days, the rental company may block your card for $300 or more. If you only have $300 of available credit, you can't use the card until the car is returned or you use another method to pay the bill.
Pay Another Way
Even if you're required to cover the car rental with a credit card, you can usually use another payment method it once you turn it in. If you have a card with $300 of available credit you can use that amount to secure the car and then pay with cash or a debit card when you return it. That frees up the $300 on hold. However, it may take up to 48 hours for the block to disappear.