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Critical Ratio Job Sequencing Worksheet for Production Schedulers

Critical ratio is a simple dispatch rule: divide the time left until the due date by the work time still needed, and run the job with the lowest ratio first. This worksheet calculates it for every open job and exports a dispatch list in Excel.

Download:

Work days needed	Slack (days)	Critical ratio
4 days	2 days	1.5
3 days	0 days	1.0909
3 days	7 days	3.3333
4 days	0 days	1
1 days	1 days	2
1 days	7 days	8

Total remaining process hours

84 hrs

Lowest critical ratio

Average slack

3 days

Jobs listed

Run the job with the lowest critical ratio first. A ratio below 1.0 means the job is already behind. Re-sort and recalculate daily, since due days, remaining hours and queue change every shift.

Generate dispatch lists straight from your ERP

Optional: we can review how open jobs, routings and due dates in your ERP could produce a daily dispatch list.

Optional. The tool and every export work without this. No spam.

How to use the worksheet

List open jobs with their work center, days until due and the process hours that remain across the routing. Add an honest estimate of queue and move time and the hours per day the job can really be worked. The worksheet computes the work days needed, the slack in days and the critical ratio. Sort the exported list by ratio, ascending, and work down it. Replace the example rows with your own jobs.

Update days until due every morning
Use remaining hours, not the original routing hours
Be realistic about queue time
Review jobs under 1.0 first thing each shift

The formulas

Work days needed = (remaining process hours + queue and move hours) / productive hours per day. Slack = days until due minus work days needed. Critical ratio = days until due / work days needed. A job due in 3 days that needs 22 hours at 8 hours a day needs 2.75 working days, so its ratio is 1.09 and its slack is 0.25 days. A ratio of 0.5 means the job has half the time it needs.

How it compares with other rules

Earliest due date ignores how much work is left. Shortest processing time clears jobs fast but starves long ones. Slack time rule looks at due date minus work, as this sheet does in column form. Critical ratio normalises the slack so large and small jobs compare fairly. It works well in job shops with changing priorities, though it needs good remaining hour data, which ERP routings and job reporting usually provide.

Common mistakes

A ratio below 1 on a job with unrealistic queue time can mislead, so check the inputs before expediting. Do not mix calendar days and working days. And remember that critical ratio only sequences within a work center; it does not check capacity, so a list full of ratios under 1 means you need more capacity or later promised dates, not a better sort.

Frequently Asked Questions

What does a critical ratio of 1.0 mean?

The time remaining equals the time needed, so the job is exactly on schedule with no slack. Anything below 1.0 means the job will be late unless it is expedited or the due date moves.

What if a ratio is negative or zero?

A negative or zero ratio means the job is already past due. Treat it as the highest priority, then decide with sales whether to expedite, split the lot or re-promise the date.

How often should I recalculate?

At least once a shift, because each hour of progress and each passing day changes both the numerator and the denominator. Many shops refresh the list at the start of every shift.

Can I use this with APS or ERP scheduling?

Yes. Use it as a simple manual check next to finite scheduling output. If the system's sequence puts a job with a low ratio late in the queue, review the rule or the inputs it uses.

Most ERP systems hold due dates, routings and reported hours. We can generate this dispatch list per work center from live data so it refreshes every shift.

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