How to Convert Recipe from Fan Oven to Conventional Oven

Most recipes specify either a fan oven or a conventional oven temperature — but what if you have the other type? Converting between the two is simple once you know the rule. Here's everything you need to know.

The Basic Conversion Rule

The standard conversion between fan oven and conventional oven temperatures is:

• Fan oven → Conventional oven: Add 20°C (or 25°F)
• Conventional oven → Fan oven: Subtract 20°C (or 25°F)

This works because the fan circulates hot air more efficiently, so a fan oven at 160°C cooks food at the same rate as a conventional oven at 180°C.

Fan Oven to Conventional: Temperature Conversion Table

• 140°C fan → 160°C conventional (320°F)
• 150°C fan → 170°C conventional (340°F)
• 160°C fan → 180°C conventional (350°F)
• 170°C fan → 190°C conventional (375°F)
• 180°C fan → 200°C conventional (400°F)
• 190°C fan → 210°C conventional (410°F)
• 200°C fan → 220°C conventional (425°F)
• 210°C fan → 230°C conventional (450°F)
• 220°C fan → 240°C conventional (465°F)

Do You Also Need to Adjust Cooking Time?

Usually, if you adjust the temperature correctly, the cooking time stays roughly the same. However:

• If switching from fan to conventional, check food 5–10 minutes earlier than the recipe states — conventional ovens can have hot spots
• If switching from conventional to fan, food may cook slightly faster due to more efficient heat circulation
• Always use visual cues (golden colour, skewer test, internal temperature) rather than relying solely on time

Gas Mark Conversions

If your recipe uses gas marks, here's a quick reference:

• Gas Mark 1 → 140°C conventional / 120°C fan
• Gas Mark 2 → 150°C conventional / 130°C fan
• Gas Mark 3 → 170°C conventional / 150°C fan
• Gas Mark 4 → 180°C conventional / 160°C fan
• Gas Mark 5 → 190°C conventional / 170°C fan
• Gas Mark 6 → 200°C conventional / 180°C fan
• Gas Mark 7 → 220°C conventional / 200°C fan
• Gas Mark 8 → 230°C conventional / 210°C fan
• Gas Mark 9 → 240°C conventional / 220°C fan

Why Your Oven May Still Cook Differently

Even with the correct conversion, ovens vary. A dial set to 180°C may actually run at 165°C or 195°C depending on the model and age of the oven. The only way to know your oven's true temperature is to use an oven thermometer.

The Oven Thermometer 2 Pack (50–300°C / 100–600°F) is a reliable stainless steel option that gives you an accurate real-time reading — essential for consistent baking and roasting results regardless of which oven mode you use.

Summary

To convert from fan oven to conventional, add 20°C. To convert from conventional to fan, subtract 20°C. Cooking time usually stays the same, but always check food visually and use an oven thermometer to verify your actual oven temperature.