What is capacity planning?
Capacity planning is answering one question: can your shop handle the work in front of it?
Not “can we squeeze it in somehow.” Not “we’ll figure it out.” Can you actually run these jobs, on these machines, with these people, and hit every deadline?
If you run a small shop with 3 to 30 machines, this is a question you answer every week. Sometimes every day. A new quote comes in. A customer wants to double their order. Someone asks if you can take on a recurring contract. Your answer to all of these depends on knowing your capacity.
Why small shops need capacity planning
Big factories have entire teams for this. They use MRP systems, demand forecasting, and complex models. You don’t need any of that.
But you do need to know your numbers. Without them, two things happen:
You take on too much work. Everything looks manageable when you say yes. Then three weeks later, every machine is overloaded, operators are working overtime, and you are missing deadlines on jobs that were supposed to be easy.
You turn away work you could have taken. If you don’t know how much capacity you have left, you play it safe and say no. That job goes to your competitor. Maybe the customer comes back. Maybe they don’t.
Both problems cost you money. Capacity planning is how you find the line between the two.
How to calculate your shop’s capacity
Start with the basics. No spreadsheet required for this first pass.
Step 1: Count your available machine-hours
For each machine, multiply:
- Hours per shift x shifts per day x days per week
Example: You run one 8-hour shift, 5 days a week, and you have 6 machines.
6 machines x 8 hours x 5 days = 240 machine-hours per week
That is your theoretical maximum. The actual number is lower.
Step 2: Subtract non-production time
Not every hour is production time. You need to subtract:
- Setup/changeover time. Most shops lose 15-25% of available time to setups. If your setups average 20% of machine time, subtract 48 hours from the 240.
- Planned maintenance. If each machine gets 1 hour of maintenance per week, subtract 6 hours.
- Breaks and shift transitions. Maybe 30 minutes per machine per day for operator breaks and shift handoffs. That is 15 hours per week.
240 - 48 (setups) - 6 (maintenance) - 15 (breaks) = 171 practical machine-hours per week
That is your real capacity. About 71% of the theoretical max. This is normal for a well-run small shop.
Step 3: Know your bottleneck
Not all machines are equal. Your capacity is really determined by your most constrained machine.
If your VMC runs at 90% utilization but your lathe runs at 40%, your VMC is the bottleneck. Adding more lathe time doesn’t help. Every new job that needs the VMC competes with everything already on it.
Identify your bottleneck. That machine’s capacity is your shop’s true capacity for any job that needs it.
Capacity planning in practice
Here is how this works day to day in a small shop:
Quoting new work
When a new RFQ comes in, before you price it, check:
- Which machines does this job need?
- How many hours on each machine?
- What is the deadline?
- Do those machines have enough open time before the deadline?
If the answer to #4 is no, you have three options: push back on the deadline, decline the job, or bump something else (which means talking to that customer first).
This takes 5 minutes if you have visibility into your current schedule. It takes 30 minutes of detective work if you don’t.
Weekly capacity review
Spend 10 minutes at the start of each week looking at your schedule:
- What is the utilization on each machine this week? If any machine is above 85%, watch it closely. If it is above 95%, something will probably slip.
- What is coming next week? Are there jobs queued up that you haven’t scheduled yet? Get them on the board now.
- Where is the slack? If a machine has open time, that is either an opportunity (take on more work) or a problem (why isn’t it booked?).
This is basic, but most shops don’t do it. They react instead of planning. Reacting works until the workload exceeds what your memory can handle.
Seasonal patterns
Most shops have busy seasons and slow seasons. Metal fabrication shops often see spikes before construction season. Assembly operations may ramp up before product launches.
Track your capacity numbers month over month. After a year, you will see the pattern. That lets you plan hiring, maintenance windows, and equipment purchases around the cycle instead of being surprised by it every time.
When to say no
Saying no to work is hard. Every job is revenue. But taking on a job you can’t deliver on time is worse than declining it.
Here are clear signals to say no (or push the deadline):
- Your bottleneck machine is already at 80%+ utilization for the period the job needs it
- The job requires a setup that would bump an existing job with a tighter deadline
- You would need overtime to fit it in, and the margin doesn’t justify the overtime cost
- You don’t have the material in stock and lead time puts the job at risk
Saying no today, with a clear explanation, keeps the relationship intact. Missing the deadline later does not.
When to buy another machine
This is the big question. A new machine is a serious investment. Here is how to think about it:
The wrong reason to buy
“We’re really busy right now.” Busy is not a reason. Busy might be a two-month spike. It might be one large order that won’t repeat. Don’t make a capital decision based on a temporary situation.
The right reason to buy
You are consistently turning away profitable work because one specific machine is maxed out, and you have already:
- Optimized your scheduling to minimize that machine’s idle time
- Reduced setup times on that machine
- Checked whether any jobs can be rerouted to other machines
- Confirmed the demand is sustained, not a one-time spike
If all four are true, it is time to invest.
The math
Add up the revenue from jobs you turned away over the last 3 months because of that machine. Annualize it. Compare that to the cost of the machine (purchase price + installation + tooling + operator cost).
If the machine pays for itself in 12 to 18 months based on the work you are already turning away, it is a good investment. You are not speculating. You are buying capacity for demand that already exists.
Compare this to how tools like MRPeasy or Katana approach capacity planning. They build it into larger ERP systems with demand forecasting and MRP calculations. That is useful for larger operations, but most small shops need a simpler approach first.
Common mistakes
1. Planning to theoretical capacity
If you have 240 machine-hours available, you do not have 240 hours of production capacity. Plan to 70-75% of theoretical. That accounts for setups, maintenance, and the unexpected.
2. Ignoring the bottleneck
Your shop’s capacity is not the average utilization across all machines. It is the capacity of your most constrained machine. Everything flows through that bottleneck.
3. No buffer for rush jobs
If your schedule is 100% full, you cannot take a rush order without bumping something else. Keep 10-15% of your bottleneck’s capacity unscheduled as a buffer. That flexibility is worth more than the revenue from filling every last slot.
4. Not tracking the data
You cannot plan capacity if you don’t know your current utilization. Start by tracking your top 3 machines for a week. That data alone will change how you make decisions.
A scheduling tool that shows machine assignments and utilization makes this automatic. You stop guessing and start seeing.
Start simple
You don’t need a capacity planning system. You need to know three numbers:
- How many machine-hours do you have per week? (After subtracting setups, maintenance, and breaks.)
- How many machine-hours are booked this week? (From your current schedule.)
- Which machine is most loaded? (That is your bottleneck.)
With those three numbers, you can answer any capacity question that comes your way. Should we take this job? Can we hit this deadline? Do we need another machine?
That is capacity planning. Not a system. Not a formula. Just knowing your numbers.