My pink wonder is as accurate as the three mercury-filled Ovu-index ones that preceded it (until they respectively got left behind in a B&B in England, broke, and in the last case, had the mercury stop moving for some reason). I think what's less accurate as I approach menopause is me. For years the before ovulation temp was 98.2 and after was 98.6. In some months that's still true, but in others it seems to change every day.