Estimate editing effort between drafts.
The draft-to-final ratio tells you how much of your first draft survived, and it is a useful diagnostic of your own process. Around 1.1 to 1.3 is typical for considered prose — some cutting, some tightening. A ratio above 1.5 means you are writing substantially more than you need and paying for it twice, once in drafting and again in editing. A ratio below 1 means the piece grew, which usually signals an under-developed draft rather than efficient writing. Editing time is estimated by summing the words reviewed across rounds, since each pass re-reads the whole piece and that is where the hours actually go.
Draft to final ratio
Ratio = draft words / final words
Editing effort
Hours = total words reviewed across all rounds / editing speed
Between about 1.1 and 1.3 for most non-fiction. Some cutting is a sign of genuine revision, but a ratio of 1.6 or more means most of the drafting effort was discarded — usually because the structure was not settled before the prose started.
Because time tracks words read, not words changed. Every round re-reads the full piece regardless of how much is edited, so three rounds on a 5000-word essay is 15,000 words of reading. That is why reducing the number of rounds by planning better saves more time than editing faster.