Operations Management and Strategic Management · Scheduling and Queuing Models

Gantt Charts and Loading in Production Scheduling

Updated 10 October 2026 · Fact-checked

A Gantt chart is a bar chart with time on the horizontal axis and machines or jobs on the vertical axis. A load chart shows work assigned to each work centre. A schedule chart shows when each job starts and ends. Loading assigns jobs to centres, often using the assignment method to minimise cost or time.

Understand Gantt Charts and Loading

Loading means assigning jobs to work centres (machines, departments or workers). Once you know which centre does which job, scheduling fixes the time: when each job starts and finishes. A Gantt chart is the simple visual tool used for both.

A Gantt chart has time along the horizontal axis. The vertical axis lists machines, work centres or jobs. Bars or lines against each row show how that resource is used over time. Henry Gantt developed it in the early twentieth century, and it is still used because anyone can read it at a glance.

There are two common forms. A load chart shows, for each work centre, the jobs assigned to it and the time they occupy. It tells you how heavily each centre is loaded and where there is idle capacity. A schedule chart (progress chart) shows each job against time. It compares planned progress with actual progress, so you can see which job is ahead or behind.

Loading can be done in two ways. Infinite loading assigns work to centres without checking capacity, so queues can build up. Finite loading assigns work only up to the capacity available, so the schedule is realistic. You can load forward (from the start date) or backward (from the due date).

When each job must go to exactly one centre and costs or times differ by pairing, the assignment method (Hungarian method) finds the allocation with the lowest total cost or time. The related topics on the Hungarian method cover its full procedure; here you need to know how it links to loading.

Key rules to remember

Utilisation of a work centre: Utilisation = Hours actually loaded ÷ Hours available × 100; Read the loaded hours from the load chart. A value above 100% means the centre is overloaded.
Idle time on a load chart: Idle time = Available hours − Loaded hours; Shows spare capacity that can take more jobs.
Assignment problem condition: Number of jobs = Number of centres (square cost matrix); If not equal, add dummy rows or columns with zero cost.
Hungarian reduction: Row reduction, then column reduction, then cover zeros with minimum lines; optimal when lines = n; For maximisation, convert by subtracting every value from the largest value, then minimise.

How to solve Gantt Charts and Loading questions

Most questions ask you to draw or read a chart, or to assign jobs at least cost. Use this order.

1Read the question and decide the task: draw a load chart, draw a schedule chart, or assign jobs optimally.
2For a chart, draw the time axis horizontally with a clear scale and list machines or jobs on the vertical axis.
3Place each job as a bar from its start to its finish. Respect the sequence and any capacity limit of each centre.
4Mark idle time and overload. Compute utilisation if hours are given.
5For assignment, check the matrix is square. Add a dummy row or column of zeros if needed. Convert maximisation to minimisation if required.
6Subtract the row minimum from each row, then the column minimum from each column. Cover all zeros with the fewest lines.
7If lines are fewer than n, subtract the smallest uncovered value from uncovered cells, add it at line intersections, and repeat. When lines equal n, assign to zero cells one by one.
8Add up the original costs of the chosen cells for the total, and state the allocation clearly.

Quickest way: Fast route for assignment and chart questions

When to use it: Use when time is short and the matrix is small, usually 3×3 or 4×4.

Do row and column reduction first, then look for rows or columns with a single zero.
Assign that zero, strike out its row and column, and repeat.
If every row and column has at least one assignment, stop. Otherwise use the line-covering step.
Always total the cost from the original table, not the reduced one.
For charts, draw the axes with a ruler and label each bar with the job name and hours so the examiner can follow it.

Common mistakes in Gantt Charts and Loading

Confusing a load chart with a schedule chart
Both look like bar charts on a time axis.
Fix: Load chart: rows are work centres, showing how much work each carries. Schedule chart: rows are jobs, showing planned versus actual progress.
Totalling the cost from the reduced matrix
Students stay in the last table they worked on.
Fix: Go back to the original matrix and add the costs of the assigned cells.
Applying the Hungarian method to an unbalanced matrix
The row and column count is not checked first.
Fix: Add a dummy row or column with zero entries to make the matrix square.
Maximising by picking the lowest numbers
The method is learnt only for minimisation.
Fix: Subtract every entry from the largest entry, then minimise. Report the profit from the original table.
Drawing bars with no scale or labels
Charts are drawn in a hurry.
Fix: Mark equal time units, label every bar and show idle time so step marks are earned.

Worked examples

Example 1

Four jobs A, B, C, D are to be assigned to four machines P, Q, R, S, one job per machine. Costs (₹) are: A: P 8, Q 6, R 10, S 9; B: P 9, Q 12, R 13, S 7; C: P 7, Q 5, R 12, S 8; D: P 10, Q 8, R 9, S 11. Find the minimum-cost assignment.

Show the solution

Row minimums are A 6, B 7, C 5, D 8. Subtracting gives A: 2,0,4,3; B: 2,5,6,0; C: 2,0,7,3; D: 2,0,1,3.
Column minimums are P 2, Q 0, R 1, S 0. Subtracting gives A: 0,0,3,3; B: 0,5,5,0; C: 0,0,6,3; D: 0,0,0,3.
Cover zeros: column P, column Q and row D... zeros in P (A,B,C,D), Q (A,C,D), S (B), R (D). Lines: P, Q, S and row D cover all zeros, which needs 4 lines only if R is covered by row D. Lines = 4 = n, so assignment is possible.
Start with single zeros. Row B has zeros at P and S; column R has a zero only at D, so D to R. Column S has a zero only at B, so B to S. Remaining rows A and C with columns P and Q: A to Q and C to P, or A to P and C to Q.
Take A to Q, B to S, C to P, D to R. Costs: 6 + 7 + 7 + 9 = 29.
Check the alternative A to P, C to Q: 8 + 7 + 5 + 9 = 29. Same total.

Answer: Minimum cost is ₹29. One optimal assignment is A to Q, B to S, C to P, D to R. A to P, B to S, C to Q, D to R is equally good.

Example 2

A work centre has 40 hours available in a week. Jobs J1 (12 hours), J2 (9 hours) and J3 (14 hours) are loaded on it. State what a load chart shows and find utilisation and idle time. Can a 6-hour job J4 be added under finite loading?

Show the solution

A load chart shows the centre on the vertical axis and a bar of 40 hours on the horizontal axis, filled by J1, J2 and J3 in turn.
Loaded hours = 12 + 9 + 14 = 35.
Utilisation = 35 ÷ 40 × 100 = 87.5%.
Idle time = 40 − 35 = 5 hours.
J4 needs 6 hours but only 5 are free. Under finite loading, adding it would exceed capacity.

Answer: Utilisation is 87.5% with 5 hours idle. J4 cannot be added within the week under finite loading; it must be moved to the next week or to another centre, or overtime used.

Exam tips

Be ready to state the difference between a load chart and a schedule chart in two or three lines; this is a frequent short-answer question.
In assignment questions, show every step: row reduction, column reduction, line covering and final allocation. Step marks depend on it.
For MCQs, remember that a Gantt chart has time on the horizontal axis and that the assignment method needs a square matrix.
Always state the total cost with the rupee sign and list the job-to-machine pairs.

Practice questions from Scheduling and Queuing Models

Gantt Charts and Loading: frequently asked questions

What is a Gantt chart in production scheduling?

It is a bar chart with time on the horizontal axis and machines, work centres or jobs on the vertical axis. It shows planned and actual use of resources over time. Managers use it to spot idle time, delays and overloads.

What is the difference between a load chart and a schedule chart?

A load chart shows the work assigned to each work centre and how heavily it is used. A schedule chart shows each job against time, with planned and actual progress. One focuses on capacity, the other on job progress.

What is machine loading?

Machine loading is the assignment of jobs to machines or work centres. Infinite loading ignores capacity limits. Finite loading assigns only as much work as the capacity allows.

How is the Hungarian method used in scheduling?

It assigns each job to one machine or worker so that total cost or time is the lowest. You reduce the matrix by rows and columns, cover zeros with lines, and assign on zero cells once lines equal the matrix size.