# Critical Ratio Job Sequencing Worksheet for Production Schedulers

> Source: https://netray.co/tools/critical-ratio-job-sequencing-worksheet
> Publisher: Netray (netray.co), AI and integration engineering for ERP and manufacturing systems.
> Section: Free Tools

## Short answer

Rank open jobs by critical ratio and slack so the most behind jobs run first. Editable table that exports to Excel.

## Category

mes-shop-floor

## Industry

Discrete Manufacturing

## Audience

- Production scheduler
- Shop floor supervisor
- Planner

## Tool

**Kind:** worksheet

**Mode:** editable

**Columns:**

#### Job number

**Key:** job

**Type:** text

#### Work center

**Key:** wc

**Type:** select

**Options:**

- Saw
- CNC mill
- CNC lathe
- Deburr
- Weld
- Paint
- Assembly
- Test

#### Days until due

**Key:** due_days

**Type:** number

**Unit:** days

**Help:** Calendar or working days to the due date, used consistently.

#### Remaining process hours

**Key:** remain_hrs

**Type:** number

**Unit:** hours

**Help:** Setup plus run for all remaining operations.

#### Expected queue and move hours

**Key:** queue_hrs

**Type:** number

**Unit:** hours

#### Productive hours per day

**Key:** hrs_day

**Type:** number

**Unit:** hours

**Help:** Hours per day the job can actually be worked.

#### Work days needed

**Key:** work_days

**Type:** number

**Expr:** (remain_hrs + queue_hrs) / hrs_day

**Format:** days

#### Slack (days)

**Key:** slack

**Type:** number

**Expr:** due_days - work_days

**Format:** days

#### Critical ratio

**Key:** cr

**Type:** number

**Expr:** due_days / work_days

**Format:** decimal

**Help:** Below 1.0 is behind schedule, 1.0 is on time, above 1.0 is ahead.

**Rows:**

**Job:** WO-10412

**Wc:** CNC mill

**Due days:** 6

**Remain hrs:** 22

**Queue hrs:** 10

**Hrs day:** 8

**Job:** WO-10415

**Wc:** CNC lathe

**Due days:** 3

**Remain hrs:** 14

**Queue hrs:** 8

**Hrs day:** 8

**Job:** WO-10420

**Wc:** Weld

**Due days:** 10

**Remain hrs:** 18

**Queue hrs:** 6

**Hrs day:** 8

**Job:** WO-10423

**Wc:** Assembly

**Due days:** 4

**Remain hrs:** 20

**Queue hrs:** 12

**Hrs day:** 8

**Job:** WO-10431

**Wc:** Paint

**Due days:** 2

**Remain hrs:** 4

**Queue hrs:** 4

**Hrs day:** 8

**Job:** WO-10436

**Wc:** Test

**Due days:** 8

**Remain hrs:** 6

**Queue hrs:** 2

**Hrs day:** 8

**Totals:**

#### Total remaining process hours

**Key:** remain_hrs

**Agg:** sum

**Format:** hours

**Summary:**

#### Lowest critical ratio

**Key:** lowest_cr

**Expr:** min_cr

**Format:** decimal

**Primary:** true

#### Average slack

**Key:** mean_slack

**Expr:** avg_slack

**Format:** days

#### Jobs listed

**Key:** job_count

**Expr:** count

**Format:** integer

**Notes:** 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.

## Content

**Intro:** 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.

**Sections:**

#### How to use the worksheet

**Body:** 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.

**Bullets:**

- 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

**Body:** 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

**Body:** 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

**Body:** 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.

**Cta:** 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.

**Faq:**

#### What does a critical ratio of 1.0 mean?

**Answer:** 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?

**Answer:** 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?

**Answer:** 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?

**Answer:** 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.

## Search terms

critical ratio scheduling, critical ratio dispatch rule, job sequencing worksheet excel, dispatch list template, job priority calculator, slack time scheduling rule, production dispatching rules, critical ratio formula

---
Talk to an engineer: https://netray.co/contact?intent=erp_ai | Machine catalog: https://netray.co/agent/catalog.json