Estimate practice time to master a piece.
Learning a piece is not uniform work. The quarter of bars that are difficult absorb most of the practice, because they need thirty or more slow repetitions to become reliable while easy bars need a handful. Splitting the piece into those two populations and costing each separately explains why a short piece with two awkward passages can take longer than a long straightforward one.
Split practice cost
Difficult minutes = bars x difficult share x repetitions x seconds / 60; easy minutes = remaining bars x 8 repetitions x seconds / 60
Calendar time
Days to master = total practice minutes / daily practice minutes
Slow and accurate first. Repetition encodes whatever you actually play, so practising a passage fast with errors makes the errors automatic. Speed is added only once accuracy is reliable.
It is a working figure for motor consolidation of a short passage, and it works best spread across days rather than done in one sitting — sleep between sessions is when the gain consolidates.