What Is Capacity Planning?
Also known as: CRP, capacity requirements planning, rough cut capacity planning
Definition
Capacity planning is the process of comparing the labor and machine hours a production plan requires against the hours each work center actually has available, identifying overloads early enough to reschedule, add shifts, or outsource.
Capacity Planning Explained
Capacity planning operates at multiple horizons. Resource requirements planning works at the sales and operations planning level, testing whether a volume plan is feasible against major resources over months. Rough cut capacity planning validates the master production schedule against a handful of critical work centers using a bill of resources. Capacity requirements planning runs after MRP and computes detailed load by work center and period from every planned and released order, using routing hours. Each level trades precision for speed and horizon.
The load calculation itself is straightforward: for each operation on each order in a period, add setup hours plus quantity times run hours, and accumulate by work center. Available hours come from the work center definition: number of machines or operators, shift hours per day, working days from the calendar, and an efficiency or utilization factor. Load divided by available capacity gives a percentage, and anything consistently over 100 means the plan is not executable as stated.
Infinite versus finite is the key distinction. Capacity requirements planning is infinite: it reports the overload but does not move anything. Finite capacity scheduling and advanced planning tools resolve overload by sequencing work within available capacity, which changes dates but produces an executable schedule. Many mid-market plants run infinite capacity requirements planning and resolve conflicts manually at a weekly scheduling meeting, which is workable when the number of constrained resources is small.
A persistent misconception is that capacity means machine hours. In plants where a specific skill, a fixture, a clean room, or a qualified inspector is the true limit, modeling only machines produces a load report that shows plenty of room while the plant misses dates. Capacity should be modeled around the actual constraint, and it is worth periodically re-identifying that constraint because it moves as product mix changes.
Why It Matters
- Capacity planning is the only check that stops MRP from handing the plant an infinite-capacity plan it cannot execute.
- Early visibility of overload converts a delivery crisis into a manageable decision about overtime, outsourcing, or rescheduling.
- Load reports quantify the business case for capital equipment far better than anecdotes about a busy machine.
- Accurate capacity data is a prerequisite for capable to promise, so investment here pays off twice.
In Practice
Worked example: a work center with two machines running one 8-hour shift, 5 days a week, at 85 percent efficiency has about 68 usable hours per week. If capacity requirements planning shows 92 hours of load, the plan is at 135 percent. The realistic options are a second shift, an alternate routing, subcontracting, or moving dates, and deciding six weeks out is far cheaper than deciding six days out.
Frequently Asked Questions
What is the difference between rough cut and detailed capacity planning?
Rough cut capacity planning validates the master production schedule against a few critical resources using a simplified bill of resources, so it runs fast over a long horizon. Capacity requirements planning runs after MRP and calculates detailed load for every work center from full routings on every planned and released order. Rough cut catches big problems early; detailed catches specific ones.
How do you calculate available capacity?
Multiply the number of machines or operators by hours per shift, by shifts per day, by working days in the period, then apply a utilization and efficiency factor to reflect breaks, maintenance, and realistic pace. A work center with three machines on one 8-hour shift over 20 working days at 85 percent yields roughly 408 usable hours per month.
Related Terms
Routing
A routing is the ERP record that defines the ordered sequence of operations required to manufacture an item, specifying for each step the work center or machine, setup time, run time per unit, move and queue time, and any outside processing.
MRP II
MRP II (Manufacturing Resource Planning) is the closed-loop extension of MRP that adds capacity planning, shop floor control, purchasing execution, and financial simulation, so the material plan is validated against labor, machine, and money constraints before release.
Work Order
A work order is the ERP document that authorizes production of a defined quantity of an item by a due date. It snapshots the bill of materials and routing, drives material issues and labor reporting, and collects actual cost for the job.
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