STEP 1. Work out the percentage difference in temperature. Start Temperature / End Temp = % Difference. For example going from 400F (200C) to 450F (230C) = 400 / 450 = 0.89 or 89%

STEP 2. Adjust Expected Time Multiply initial time by the % Difference Back to our example, if something takes 60 minutes at 400F (200C), 60 minutes x 0.89 = 53 minutes.

STEP 3. Add a safety margin This isn’t an exact science, and you don’t want to burn dinner, so I check earlier just to be sure. For our example if the new calculated time is 53 minutes, I’d check after 50 minutes.

Other factors to consider when adjusting cooking times for different temperatures. 1. Opening the oven. Every time you check and open the oven door, the temperature in the oven drops. Which will increase the cooking time. This can result in you checking, opening, checking, opening and things ending up taking significantly longer than planned. 2. Space around the food If you have equal amounts of say veggies for roasting and cram one sample into a small roasting dish but spread the other sample out on your largest rimmed baking sheet, there will be a significant difference in the time each takes to cook. The more space, the easier it is for the heat to penetrate and the quicker the cooking time. 3. Shelf Height / Position in the Oven Even in my fan assisted oven, things cook quicker on the top shelf than they will on the bottom.

Can I cook something at a higher temp for a shorter time? Absolutely! I do this all the time.

Can I bake something at a lower temperature for longer? ABSOLUTELY! If you have more time cooking at lower temperatures can be great because you will get more even cooking. Avoiding the burnt edges on your cake and the under baked middle (which sinks as it cools) is an excellent idea.

What happens if you bake at 350 instead of 400? It’s just going to take a little longer. From our conversion chart above, 350F instead of 400F will take 1.14 more time. So something that takes 30 minutes at 400F will take 34 minutes at 350F. Or for my fellow metric system users. Cooking at 180C instead of 200C will take 34 minutes instead of 30 minutes.

How to cook 2 things in the oven at the same time at different temperatures It’s simple. Use the oven set point for the most delicate item or for the one with the lowest temp. And expect the other item to take longer than normal. Also put the more delicate / lower temp dish on the lower shelf as well. For example. If I wanted to cook a cheesecake at 350F (180C) and a lasagna at 400F (200C). The cheesecake would be the more ‘delicate’ dish because it will curdle if over baked. So I would set the oven to 350F (180C) put the cheesecake on the lower shelf and the lasagna on the top. Then when the cheesecake was cooked. IF the lasagna needed longer I’d increase the temperature to finish it more quickly.