Your professional image is comprised of a myriad of elements: appropriate verbal communication, effective written communication, appearance, etiquette, and the list goes on. Some of the most powerful elements that contribute to how you are viewed professionally have to do with how you manage time. It’s not that colleagues and team members necessarily notice how you spend your time, but they are keenly aware of whether or not you complete a promised task that their project needs before it can proceed. They, and their own professional image, are impacted by your behavior and, over time, that behavior, whether positive or negative, will affect how they see you and how they value your input and expertise.

There are countless time management tools available that, theoretically, help you manage your time. As often as not, though, setting up a system and learning to use it sucks up precious hours and can give you an unrealistic impression of what you should  be able to accomplish. A more effective strategy might be to first take a pragmatic look at the time truly available to you so that you are able to set reasonable deadlines for specific tasks and projects.

So, you set up a grid of 40 hours and divide your tasks and projects into the little half hour squares–right? Wrong. The fact is, you don’t own all those 40 hours. Your managers and team mates will claim some of them. And then there’s attending to client needs and trouble shooting unplanned problems. The time that you own is what’s left after all those workplace realities are tended to.

How Much Time Do You Own?

Everybody’s available time varies but a good starting point to understanding how much time is actually available for projects is knowing how time is used in the average workplace. A 2012 McKinsey Global Institute Study looked at how work time is spent. It might be surprising to learn that 28% of the work week is spent reading, writing, and responding to email. That’s 2 hours and 14 minutes each day that is not available for working on your project.

Here’s how the study found that the hours in the average work week are used:

With this information you can see that the 40 hour grid that you thought you could use to divvy up your projects has shrunk to only about 15 1/2 hours. It begins to answer that end-of-the-day question, “Where did the time go?”

It’s tempting to think you can simply set aside 6 hours a day for your projects, zip through email, and brush off a colleague’s spontaneous visit to your cubicle, but the fact is, careful attention to email results in thorough, professional responses and brainstorming with colleagues often leads to innovative problem solving. Cutting down on work-related interaction could cut you off from the sharing of information that is essential to being a productive member of your organization.

Instead, embrace this information and use it when scheduling your work. You might still want to use that ubiquitous grid, but designate only 3 hours each day or 15 hours each week as time that is available for moving your projects forward.

With a realistic sense of the time you own, you’ll find that you stop over-promising and are able to complete tasks and bring in projects on time. You will be viewed as a professional who can be counted on to consistently deliver what is promised.