Loads of different ones, 1 unit is a good starting point, then tweak to suit, adjusting for carb size, gi of mask, activity, illness etc.
If you go to low, try 1 ~12 next time, too high try 1~8. No set answer.
Other factors to be wary of is you're of day, often people have diff ratios at diff meal times. Also if you miss a meal may impact your ratios fur the next one
I didn't know that if u miss a meal it impacts the next one. I'm about to go up to 2 units per 10g for morning and lunch. Seems like a lot to me but I keep getting ridiculous highs. It's really getting me down but I see my nurse next week!