Here's how to convert Celsius to Fahrenheit:

Formula:

* °F = (°C × 9/5) + 32

Calculations:

* 18°C: (18 × 9/5) + 32 = 64.4°F

* 26°C: (26 × 9/5) + 32 = 78.8°F

Therefore, 18-26 degrees Celsius is equivalent to 64.4-78.8 degrees Fahrenheit.