While the relationship between workload and performance may seem to be a matter of common sense, the study of workloads is a relatively new field. In fact, the word "workload" didn't even appear in dictionaries until the 1970s. Even today, workload means different things to different people and the amount of work one has and one's productivity are influenced by many different factors. The common belief that people will take eight hours to do a six-hour task if they are given the chance simply isn't true — at least not in all cases.
TL;DR (Too Long; Didn't Read)
To calculate workload, add up all of the tasks that need to be done each day and how long each will take.
Workload: Theory and Practice
One popular theory, from O'Donnell and Eggemeier in 1979, suggests that the relationship between workload and performance can change depending on the difficulty of the tasks being done. As tasks become more difficult, performance will go down, even if the workload remains the same. Another theory proposed by Hart and Wickens in 1990 links personal strategies used by employees in dealing with workload as a major contributor to performance. People tend to manage their time and effort to maintain a reasonable amount of workload, by rescheduling less important tasks.
While the theories may have direct implications for your business, the most important thing to keep in mind is that tasks and your employees' approaches to those tasks will vary. A highly-motivated employee will perform better than an under-motivated one. Simply increasing or decreasing the workload will not in itself always change performance.
How to Measure Workload
First, determine what the job's tasks are and their frequency. Types of workloads and their tasks can be categorized by how often they are done. Most tasks need to be done daily, while others may be weekly, monthly or even annually. A custodian, for example, may vacuum and mop daily, dust once each week, but wash windows monthly. Employees at a call center may be talking to customers and filling out support tickets many times each day, while filling out reports weekly and meeting with their manager monthly.
Second, calculate the times each task should take. Accuracy is extremely important, particularly for short tasks that need to be performed multiple times each day. If a task takes 55 minutes, rounding it up to one hour should be okay, but if a phone call at a call center takes four minutes, rounding it up to five minutes will mean your workload calculation will be off by 20 percent!
Third, factor in some wiggle room. Human beings aren't machines and it's the wiggle room between tasks that will often determine whether or not a workload is too little or too much. You can factor in time after each task, or factor in time per hour or per shift, like five or 10 minutes per hour, depending on how repetitive or strenuous the tasks are.
Fourth, add up the times the work will take for a period of time, such as a month a quarter or a year. Divide this by the number of hours the person works to determine if the workload is too high, too low or a healthy amount.
Gathering Data on Tasks
The more data you have, the more accurate your calculations will be. If you have work reports detailing how much was done each day, then use the past three months of reports to average out what the daily amounts were. Machinery or technical equipment may tell you how many times a task was done since it was installed, just as an odometer tells you how many miles a car has been driven.
If you don't have the data you need, another option is to monitor employees yourself or have them monitor themselves. There are many apps available today for performance monitoring that you can use. Basecamp, for example, allows you to set up to-do lists and look at the time taken between each task. Alternatively, you can use a spreadsheet program like Excel or Google Sheets to create a list of tasks and have the program record the time each task was checked by the employee.
Another option is to use industry standards provided by groups or associations in your industry. This may be the best option if you are starting a new project or a new business and don't yet have your own data to work with. If you are starting a commercial cleaning company, for example, the Official ISSA 447 Cleaning Times guide will give you a list for average cleaning times.