I have decided to try charting my temps to help with knowing when my ovulation is. I bought a regular thermometer and already I am having wildly varying temps. Do you have to buy a BBT for it to be correct for charting purposes?
The BBT will give you your temp to the hundredth degree rather than a regular BBT will only give to the tenth. Its helpful to have the extra info to be accurate on your chart. For example, when your temps shift when you Ovulate, most charts will show a .04 rise (at least, but some less, around .02.) Without that extra decimal point, it wont show the shift. But if your regular thermometer has it to the hundreth, then you are covered.
Gee that was a long, rambling answer but hope it helped.