There are 16 words that start with 'subto'.
| subtone | subtones | subtonic | 
| subtopia | subtopic | subtotal | 
| subtonics | subtopias | subtopics | 
| subtorrid | subtotals | subtotaled | 
| subtotally | subtotaling | subtotalled | 
| subtotalling | ||
Note: These 16 words that start with 'subto' are found from the USA & Canada version of the tournament Scrabble word list.