Celsius and Fahrenheit conversion formulas may be difficult for you to remember or keep straight. They initially were for me when I was studying for the PTCB Exam, so out of necessity I looked for a work around to use in a pinch.

The Ball-parking system below is very simple, yet surprisingly helpful. 30 degrees C is really as high as you can go using this system. Luckily, It covers just about everything you need for the purpose of the test you are taking.

Here's a low budget video of how to ball-park Temperature Conversions.

Here are instructions :

✓ Draw a vertical line (about 6”).

✓ Put a small circle at the bottom so it looks like a thermometer.

✓ Just above the circle, draw a horizontal hash mark.

✓ Draw 3 more hash marks above that about 1” apart.

✓ Put a C on the Left and a F on the right at the top of the line.

✓ On the lowest hash mark, write 0 on the left and 30 on the right.

✓ On the next hash mark up write 10 on the left and 50 on the right.

✓ On the next hash mark up write 20 on the left and 70 on the right.

✓ On the next hash mark up write 30 on the left and 90 on the right.

✓ Do you notice the pattern?

✓ Each time C° goes up 10°, F° goes up by 20°.

Try some examples from your practice exams and see what you think.

** Disclaimer:
Using this ball-parking system is really just making a “better guess” at which answer is correct on a test. It should only be used if you cannot remember the formulas and should never be used in the workplace. The answer the system gives may be “close” to correct, but it's really just in the “ball-park”. Think of it as an extended part of your process of elimination. It may also be used to cross check answers you get using the formula.