What it does. Takes a budget and turns it into a range: how many options, how deep, in which roles and at which price rungs. The plan is where strategy becomes units — and where most buying mistakes are made before a single sample is seen.
Inputs. Sales target for the category and season; target margin; last season's sell-through by role and rung (or a benchmark); average selling price; planned markdown rate; number of stores or channels; lead times.
Steps.
1. Money. Convert the sales target into units: sales ÷ average selling price = units to sell. Divide by the target sell-through (never by 100%) to get units to buy. This is the open-to-buy in units; multiply by average cost for the cash.
2. Roles. Split the units across core / fashion / image. Start from last season's actual split and the strategy: a stable brand around 70/25/5, a fashion-led one nearer 40/50/10. Write the reason for any change.
3. Rungs. Within each role, split across entry / core / hero. Check the ladder: three rungs, visible reasons, hero thin.
4. Width vs depth. Decide the number of options per role and rung; depth = units ÷ options. Test the depth against the size curve: an option that cannot cover a full size run in every store is too shallow to exist. Cut width before cutting depth.
5. Timing. Phase the buy across the season (drops); attach a lead time to each phase; mark the last date a reorder can still arrive in time.
6. Risk. For every fashion and image option, write one line: the signal it rests on (from your trend work) and the exit if it fails (markdown depth and week).
7. Check. Total units, total cost, planned margin after planned markdowns. If the margin misses, go back to width (step 4), not to price (step 3).
Common errors. Dividing by 100% sell-through. Adding options because each one "seems good" — width without depth. Planning markdown at zero. Copying last season's split without a reason. Ignoring the size curve until the buy is placed.
What a good output looks like. One table: role × rung, with options, depth, units, cost, planned ST% and markdown; a phasing line; a risk line per fashion option. A reader should see in one minute where the money is, where the risk is, and why.