If you go ask a dozen different people how much you should tip a pizza delivery driver, you may receive some strong opinions.

Many people have strong opinions on what the “right” amount to tip is, but there are already standards for how much is the right amount.

According to CNN Money and Tipping.org, a food delivery person should be tipped 10% of the bill, excluding taxes. The tip should be at least $1 if the order costs less than $10, and the tip should be increased to 15%-20% for particularly difficult deliveries.

When it comes to your own personal choice, following the advice of the experts would be a good move. A tip of 10% for most food deliveries is completely fair, but it’s important to consider extenuating circumstances. If the weather is nasty outside, the distance is very far, or you took a while to greet them, their job was made more difficult and costly, so a larger tip should be in order.

To keep things simple for the delivery driver, it’s typically most appreciated when you tip in cash. The New York Times recently exposed DoorDash for using its tip feature to subsidize workers’ pay. The company changed its policies after the report, but apps are usually not the most honest or transparent when it comes to tips, and the same can be said of point of sale systems for credit cards.