Volumes and case counts: how many cases, how often?

The case count says how often a process runs in a given period, for example 1,000 invoices a month or 120 orders a week. Without it you can describe a process, but you cannot say what it costs per year, how many people it needs or where it overloads. Collect it per period, note peaks separately and record the shares at every decision.

Why the volume matters more than the diagram

A process map shows what happens. The volume decides whether it matters. A step that takes ten minutes is irrelevant at twenty cases a month and fills a full-time position at two thousand. Cost per year, staff demand, utilization and the bottleneck all depend on the case count; the lead time of a single case does not.

That is why a sound process analysis collects a small set of figures alongside the drawing: cases per period, the share of cases at each decision and, where relevant, the share of each case type. In ERP and digitalisation projects these figures are usually called the volume figures or transaction volumes, and they belong in the requirements specification just as much as the process description.

Three ways to get the case count

In practice you rarely measure from scratch. Use the best source available and say which one you used:

• System report: the number of invoices posted, orders entered or tickets closed per month, taken from the ERP, the document management system or the ticket tool. This is the most reliable source for anything that leaves a trace in a system.
• Tally sheet: for work without a system trace, such as phone queries or paper requests, the people doing the work make a mark for every case over two to four typical weeks. Simple, but agree beforehand what counts as one case.
• Estimate: in the mapping session, ask "How many of these do you handle on a normal day? And in a bad week?" An estimate with a range is far better than a blank field, and it can be replaced by a report later.

Peaks, seasons and the normal period

Office work is rarely even. Invoices pile up at month end, applications arrive after a job advert goes online, complaints follow a delivery problem. An average hides this. Record the normal volume as the basis and note the peak separately: "1,000 invoices a month, in the last week of the month about a third of them".

For staffing decisions the peak is often the more important figure, because a team that copes on average can still be overloaded for one week every month. A practical approach is to calculate the process twice, once with the normal and once with the peak volume, and compare utilization in both. The staffing calculator does this in seconds.

Converting between periods

Volumes come in different periods: per day, per week, per month or per year. The app stores the case count with its period and converts it using the working days per year (default 220, the days left after weekends, public holidays and annual leave) and the working hours per day (default 8).

Shares at decisions are part of the volume

The case count alone tells you how many cases enter the process. The shares at decisions tell you how many take each path. In the worked invoice example, 20% of invoices are incomplete and go back to the supplier, and 30% are above €5,000 and need an approval. Only with these shares can the app work out that the check step runs 1.25 times per case and the approval 0.3 times, which is the basis for correct times and costs. How this works in detail is explained in Branches and loops.

Ask for shares the same way as for volumes: "Out of ten invoices, how many are incomplete?" People find ratios of ten much easier to estimate than percentages.

Volume figures in ERP requirements

When a process is mapped ahead of an ERP selection or a workflow project, the volume figures are a requirement in their own right. A vendor needs to know whether the system must handle 50 or 5,000 invoices a month, how many order lines a typical order has and how often exceptions occur. Typical entries are:

• cases per period for each core process, with normal and peak volume
• shares of case types and exceptions, for example standard orders, custom-made orders, export orders
• number of people and roles involved, and how much of their time goes into the process
• documents and forms per case, and which of them arrive on paper

Try it with the purchasing template

The purchasing template starts with 500 requisitions a month and contains two decisions with shares: 30% of requisitions are above €1,000 and need approval, and 10% of those are rejected. Change the case count in the settings and watch cost per year, staff demand and utilization follow immediately, while the lead time of a single case stays the same. That is the clearest way to see what the volume does and does not influence. For the step from volume to people, continue with Staffing calculation.

Frequently asked questions

Keep learning