Working out roll widths and wastage in your head is how you buy 8% too much carpet — or 5% too little and make a second trip to the wholesaler on a Saturday.
Drop the rooms in (or pull them from a walkaround scan). Hint lays the rolls, shows live efficiency %, flags reusable offcuts, and recalculates price as you swap widths — so you stop guessing and start defending margin.
Free to start. Open it and have a go — pay only when it's pulling its weight.