Order Backlog Coverage (Weeks) and Book-to-Bill Calculator
Backlog coverage tells a plant how many weeks of work are already on the books, and book-to-bill tells whether that cushion is growing or shrinking. Together they feed capacity, hiring and lead-time decisions.
Your numbers
Unshipped, unbilled value of open sales order lines.
Trailing 8 to 13 week average of shipments.
Trailing average of bookings, net of cancellations.
What the plant can ship per week with current resources.
Your results
Backlog projections assume steady bookings and shipments. Seasonality, cancellations and pricing changes will shift the actual path.
Projected backlog vs weeks ahead
Sweeps Projection horizon from 1 to 52, holding your other inputs fixed.
Backlog by customer and promise date, on demand
Optional: see how open order lines could be summarised from your ERP without a manual report.
Optional. The tool and every export work without this. No spam.
How to use the calculator
Enter open backlog from the sales order or order book report, along with trailing average weekly shipments and new orders. Add your maximum weekly shipping capacity to see how utilised the plant is. The slider sets the projection horizon, and the chart shows where backlog heads if trends hold.
- Use the same currency basis for all four values
- Net cancellations out of bookings
- Exclude blanket order releases that are not firm
The formulas
Coverage in weeks = backlog / average weekly shipments. Book-to-bill = orders in period / shipments in period. Projected backlog = current backlog + (weekly orders - weekly shipments) x weeks, floored at zero. Coverage at maximum capacity uses capacity in place of shipments and shows the best-case time to clear the book.
Reading the result
A book-to-bill above 1 with utilisation near 100 percent suggests growing lead times and a need for more capacity or overtime. A ratio below 1 with long coverage can be an early warning of falling demand, before shipments drop. Coverage that exceeds the quoted lead time means customers are probably already being told a date you cannot meet.
Common mistakes and ERP notes
Mixing orders at list price with shipments at net price distorts the ratio. Including long-dated lines that ship years out inflates coverage; consider a 12 month cut-off. In an ERP, backlog comes from open order lines by promise date, and bookings from order entry date less cancellations, so confirm that both reports use the same filters.
- Compare coverage by product family, not only in total
- Watch the age of backlog lines past promise date
- Use a trailing average, not a single week
Frequently Asked Questions
What does a book-to-bill ratio above 1 mean?
It means new orders exceed shipments in the period, so backlog is growing. It is often read as a leading indicator of future revenue, provided the orders are firm and not padded by long-dated releases.
How many weeks of backlog is healthy?
It depends on the business. Make-to-stock shops may hold two to four weeks, while engineered-to-order and aerospace suppliers hold many months. Compare it with your quoted lead time and capacity.
Should backlog be measured in dollars or hours?
Hours of load at the constraint work center are more accurate for capacity planning, because mix changes the dollars per hour. Dollars are fine for management reporting and book-to-bill.
How do cancellations affect the result?
Subtract them from bookings, or they overstate book-to-bill and the projected backlog. Track cancellation rate as its own metric in the monthly review.
If backlog and bookings come from separate reports, we can show how an ERP agent could answer coverage by customer or product family in plain language.
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