Separate three different questions
First, identify the temperature unit. Second, identify the cooking method used in the recipe. Third, check the behaviour of the programme on your oven. These are distinct questions even when an oven display puts them in the same place.
The calculator can answer the first question precisely. Converting 180°C to 356°F says nothing about whether the original recipe expected a fan or whether your oven will automatically adjust the setting.
Check automatic conversion
GE’s convection guidance describes a common 25°F reduction and notes that many of its ovens perform the adjustment automatically. That is manufacturer guidance with a model context, not a universal instruction for every oven.
Read your own manual before applying an additional reduction. If the appliance already changes a entered recipe temperature, a second manual adjustment could produce an unintended setting. Check what the display represents.
Keep the recipe details together
Note the recipe’s stated oven mode, temperature, shelf position and vessel. If an instruction is unclear, look for the author’s notes before deciding it needs conversion.
When you record an adapted version, include the oven model and programme alongside the chosen setting. A number without those details is difficult to reuse or compare later.
Temperature arithmetic does not predict the dish
A convection adjustment is not a Celsius-to-Fahrenheit formula and it does not calculate cooking time. The shape and quantity of a dish, its container and the recipe method need their own consideration.
Use the published method and the appropriate appliance guidance to check progress. If you regularly prepare the same recipe, a clear note of the setting that worked in your equipment is a better reference than repeatedly guessing from an unexplained conversion chart.