The relationship between Celsius and Fahrenheit is linear, based on the equation F = 1.8 x C + 32 Because of this, the graph of Celsius to Fahrenheit will be a straight line. To draw this graph, first set down axes that represent Celsius and Fahrenheit, and then find the points where the two correspond.
Draw Your Axes
Pick a point on your graph paper where two lines intersect. Using your ruler, draw over the two lines that cross at this point. These are your axes, which will show the temperature in each temperature scale. The point where the two lines cross represents zero degrees Celsius and zero degrees Fahrenheit.
The horizontal line represents the number of degrees Celsius -- to the right of the zero point, it shows positive temperatures; to the left, it shows negative temperatures. The vertical line represents the number of degrees Fahrenheit. Above the zero point, it shows positive temperatures; below the zero point, it shows negative temperatures.
Choose Your Scale
Before you can begin graphing, decide how much distance each line on your graph paper will represent. For instance, if you choose each line to be a distance of 10 degrees, the first vertical line to the right of the zero point will be 10 degrees Celsius, the next 20 degrees and so on. Similarly, the first vertical line to the left of the zero point will be negative 10 degrees Celsius. You could also use increments of 4 degrees instead, so the first line to the right of the zero point represents 4 degrees Celsius, the second represents 8 degrees and so on. Having each line represent 4 degrees is useful, since the temperatures where Celsius and Fahrenheit correspond are multiples of 4 in both scales.
Label each vertical line that intersects the horizontal axis with the corresponding Celsius temperature; label each horizontal line that intersects the vertical axis with the corresponding Fahrenheit temperature.
Draw Three Points
Using your two axes, draw three points on your graph that show how Fahrenheit and Celsius correspond. Pick a Celsius temperature on your graph, then find the corresponding Fahrenheit temperature. Draw a point on your graph where the two temperatures intersect. Remember:
F = 1.8 x C + 32
However, there are some convenient points you can use on your graph if you don't feel like doing this calculation. At 0 degrees Celsius -- water's freezing point -- Fahrenheit is 32 degrees. If you're using a larger scale, water's boiling point is 100 degrees Celsius and 212 degrees Fahrenheit. There is also one temperature where Celsius and Fahrenheit are equal to each other. Negative 40 degrees Celsius is also negative 40 degrees Fahrenheit.
Connect Your Points
You now should have three points on your graph. The relationship between Celsius and Fahrenheit is linear, which means a graph of Celsius to Fahrenheit will be a straight line. Place your ruler over the three points you've drawn and draw a line going through the three points. If your three points do not line up, re-check your calculations and how you numbered the axes of your graph.