Most project managers think resource loading fails because Microsoft Project is complicated. The truth is simpler—and more frustrating. You’re probably breaking a fundamental rule you didn’t even know existed, and it’s causing your carefully planned schedules to fall apart in ways that seem random but are actually completely predictable.

Here’s what’s happening: When you assign resources to tasks, Microsoft Project doesn’t just look at your task dates and resource availability separately. It calculates the intersection of your task calendar and each resource’s individual calendar to determine when work can actually happen. Miss this concept, and you’ll spend hours scratching your head wondering why your resource assignments don’t match your expectations.

When Simple Resource Loading Actually Works

Before we dive into what goes wrong, let’s establish what “easy” looks like. Resource loading in Microsoft Project is straightforward when everything aligns:

Fixed duration task with clear start date
Resources using the same calendar as the project
Flat work contours with no exceptions
Assignment dates that match task dates perfectly

In this ideal scenario, Microsoft Project behaves exactly as you’d expect. Bob and Ned each work their assigned hours across the task duration with predictable daily allocations. Everything works smoothly because there are no calendar conflicts to resolve.

But real projects rarely stay this simple.

The Calendar Intersection Reality

Here’s where things get interesting. Microsoft Project supports three types of calendars, and understanding how they interact is crucial:

Base Calendars can be used as project defaults or assigned to specific tasks. Think of these as templates that define working hours, breaks, and exceptions.

Task Calendars override the project default for specific tasks. You might use a different task calendar for work that happens on alternate schedules or requires 24/7 operations.

Resource Calendars are assigned to individual people and may include personal exceptions like vacation time, training, or different work schedules.

The critical rule: Available working hours are the intersection of the task calendar and resource calendar working times.

A Real-World Calendar Conflict

Let’s see this in action with a scenario that trips up many project managers:

Your task uses a 9-80 alternate schedule:

9-hour shifts Monday through Thursday (9 AM to 5 PM)
8-hour shifts on alternate Fridays (ending at 4 PM)
Fridays off on alternate weeks

But your resources Bob and Ned follow the standard calendar:

Two 4-hour shifts daily with a lunch break from 12-1 PM
Standard Monday through Friday schedule
No alternate Friday schedule

When you assign Bob and Ned to this task, Microsoft Project calculates the intersection:

Lunch breaks (from their resource calendars) AND
Alternate Fridays off (from the task calendar)

The result? Bob and Ned get both the lunch breaks and the alternate Fridays off, even though your task calendar assumes full 9-hour days Monday through Thursday.

Different Resources, Different Results

Now add Sally to the same task. Sally’s base calendar matches the 9-80 alternate schedule used by the task, but she has a personal exception for National Guard training during the week of July 21-25.

Why are Sally’s hours different from Bob and Ned’s?

Sally’s base calendar is the 9-80 calendar, so she doesn’t take lunch breaks Monday through Thursday
She works the full 9-hour shifts that the task calendar expects
But she’s completely unavailable during her National Guard training week

Same task, three different working patterns, all because of calendar intersections.

Why This Breaks Your Plans

When calendar intersections don’t align with your assumptions, you get:

Unexpected task duration changes
Resources that appear overallocated when they shouldn’t be
Work that spreads across more days than planned
Assignment dates that don’t match your task dates
Hours that don’t add up to what you expected

The frustrating part? Microsoft Project is doing exactly what it’s designed to do. It’s just following rules that most users never learned.

Beyond Recognition: The Control You’re Missing

Understanding calendar intersections is just the beginning. There are specific techniques for:

Setting exact assignment hours down to the decimal
Controlling precisely when and how much a person works on each task
Troubleshooting when assignments don’t align with task dates
Managing complex resource conflicts across multiple projects
Using advanced work contours to shape resource loading patterns

These techniques exist within Microsoft Project’s native functionality—no Excel workarounds required.

The Bigger Picture: Stop the Excel Madness

Here’s a sobering reality: Over the last 40 years, millions of people have spent billions of hours recreating Microsoft Project’s resource management capabilities in Excel because they don’t understand how to use the tool’s actual features.

The irony is profound. Project managers abandon Microsoft Project’s sophisticated resource management capabilities to build elaborate Excel worksheets that attempt to replicate what the software already does—and does better—if you understand the rules.

Master Resource Loading Like a Pro

Eric Christoph brings unique expertise to this topic. As Corporate EVM Subject Matter Expert for L-3 Communications, he implemented multiple EIA-748 Earned Value Management Systems and helped build baseline plans for over 100 projects worth more than $400 billion. His experience spans both the theoretical framework and practical implementation challenges of resource management at enterprise scale.

In his upcoming live session, “Resource Loading Like a Pro: Mastering Microsoft Project Resource Management,” Eric will provide hands-on demonstrations of the advanced techniques that give you precise control over your resource assignments—techniques that most project managers never discover.

Session Details:

Date: Wednesday, July 2
Time: 12:00 PM – 1:00 PM EDT
Platform: Live on Zoom
PDU Credits: 1 PMI PDU (Ways of Working)

What You’ll Learn:

How calendars (task, base, and resource) impact your resource availability
What really happens when your assignments don’t match your task dates
How to set your assignment hours and dates exactly
How Project manages TimeScaleValues and Work Contours
Advanced troubleshooting techniques for complex resource scenarios

If you’ve ever thought, “Why won’t MS Project just do what I tell it to?” Eric’s session is your shortcut to making that happen—with fewer headaches and no more spreadsheet gymnastics.

Live events and on-demand replays are exclusive for MPUG members. Join today for just $14.75/month.

Elevate your project management skills and propel your career forward with an MPUG Membership. Gain access to 500+ hours of PMI-accredited training, live events, and a vibrant online community. Watch a free lesson and see how MPUG can teach you to Master Projects for Unlimited Growth. JOIN NOW