You've outgrown your roaster when the coffee you sell each month no longer fits the roast days you're willing to work. That's a division, not a feeling. The long days and the batches that stop matching are symptoms of a number nobody makes you compute. This article computes it.
Key takeaways
- You've outgrown your roaster when your monthly volume needs more roast days than you're willing to staff.
- The two inputs are your comfortable charge weight and your real cycle time, and you own both already.
- Adding roast days is the first capacity to try, and it runs out at labor, heat and consistency.
- A bigger machine is one of three answers, and most published advice prints only that one.
The threshold is a roast week, not a feeling
Search this question and you get two kinds of page. One lists warning signs: longer schedules, rising maintenance, batch results that drift. The other hands you both halves of a calculation, tells you to work out how many hours your orders take on your machine, and stops there. Nobody multiplies, so nobody arrives at a threshold.
The threshold isn't a pound figure and it isn't a machine size. It's a comparison between the roast hours your monthly volume requires and the roast hours your week contains. If your volume needs 60 roast hours a month and you'll run three eight-hour roast days a week, you have room. If it needs 120, you don't, and tightening your turnaround won't close a gap that size.
Here's the honest concession. A machine running a full week isn't automatically too small. Plenty of roasteries run five production days on a small drum deliberately, because the machine is paid for and the roast day is the part of the business they want to keep. Too small means too small relative to the week you're willing to work, so the threshold is partly your judgment. What it depends on is exactly two things: the hours your volume demands, and the hours you'll staff.
Your machine's real number is pounds per roast hour
Three inputs produce that number, and you already hold two of them.
The first is your comfortable charge. Roast Magazine reports what the trade believes about batch size: a maximum generally suggested at 80 percent of drum capacity, and a minimum that Kat Melheim describes as disputed, at 20 percent, 25 percent or even 40 percent. The disagreement is the useful part: a trade that can't settle its own floor won't hand you a figure for your drum, your burner and your green. Use what your machine holds well, which you already know. Most small roasteries keep a 6 to 10 kilo drum below its rated load. The production roaster in our lab is a 15 kilo and we charge it to the top, a decision about that machine and not a rule for yours.
The second is your cycle time, door to door. Not the roast. Time it from charge to the moment the drum is ready for the next batch, with cooling and the between-batch protocol counted in. This is the input the field never asks you for, and the one you can measure this afternoon with a timer.
Then multiply and divide twice. Charge weight times the complete cycles you finish in an hour gives pounds per roast hour. Monthly green volume divided by pounds per roast hour gives roast hours per month. Those hours divided by the length of a roast day you actually work gives roast days. Hold that figure against your calendar. It's the only version of too small that means anything.
The cheapest extra capacity is a longer roast week
Before you buy anything, add roast hours. It needs no purchase and no lead time, and for a roastery a few hundred pounds a month past comfortable it usually settles the question. Not one of the pages ranking for this query tells a roaster to try that first.
It runs out in three places.
- Labor comes first. A roast day is a person's day, and the second one isn't free. If that person is you, the capacity you just added comes out of work you weren't getting to anyway.
- The machine is second. Scott Rao describes the between-batch protocol as a way to reset the thermal energy of the roasting machine and to keep chamber surfaces from creeping hotter through a roasting session. A longer session is a harder session to hold steady, and the protocol that corrects for it costs time you didn't put in your cycle.
- Consistency is third, and it's the one you can't see in the tray. Roast color here is graded on a spectrometer batch by batch rather than judged by eye, which is the only way to learn whether the tenth batch of a long day is still the same coffee as the first.
This is where the second-machine question lands. Two small drums buy parallel batches and a second operator's hours; one larger drum buys fewer cycles for the same pair of hands. If labor is the constraint, the larger drum wins.
A bigger machine is one of three answers, and the field prints one
Once you have a number, a bigger machine is one of three answers to it. Buy more drum. Have somebody else roast the volume you can't. Or roast that volume yourself on somebody else's machine. Add the longer week above and your real menu has four items. Almost everything published on this question prints one.
A toll roasting arrangement covers the second: your green, somebody else's roastery, somebody else's hands. Renting time on a production roaster covers the third, which is capacity without a purchase and with your own hands still on the controls. We rent that capacity here, which is worth stating plainly before you weigh it.
Two of those are wrong for some readers, and I'd rather name who. If roasting is the thing you actually sell, and the profile and the sourcing are what your customers came for, handing the roast to a contract roaster removes the product. Below a certain monthly volume none of the four is worth the trouble, and buying roasted coffee wholesale from a roastery you trust is the honest answer; the lineup is one place to look. If what's straining is green inventory rather than roast capacity, how long green coffee lasts is the more useful piece.
One boundary, because two questions look alike and aren't. If you've never owned a roaster and are choosing a route to a first bag, that's the earlier decision, and starting a coffee brand without buying a roaster is written for it. This article assumes the machine is already yours and the volume has grown past it.
Questions we get about outgrowing a roaster
How do I know when my coffee roaster is too small?
You know when your monthly volume needs more roast hours than your week can hold. Work out pounds per roast hour on your own machine, divide your monthly green volume by it, then divide again by the hours in a roast day you work. If that's more days than you'll staff, the machine is too small.
How much coffee can a roaster produce in an hour?
Measure it, because no published figure will be true for your machine. Charge weight times the complete cycles you finish in an hour gives pounds per roast hour. A cycle runs from charge to the moment the drum is ready again, cooling and between-batch protocol included. Rated drum capacity alone overstates real output every time.
How full should you charge a coffee roaster?
Charge what your drum holds well, which is usually short of its rated capacity. Roast Magazine reports a maximum batch generally suggested at 80 percent of drum capacity, and a minimum disputed at 20 percent, 25 percent or even 40 percent. A floor the trade can't agree on isn't a number to run production against.
Can I add roast days instead of buying a bigger roaster?
Yes, and it's the first thing to try. Adding roast hours needs no purchase and no lead time, and it settles the problem for a lot of roasteries a few hundred pounds a month past comfortable. It stops working at three points: labor, the heat a long session builds, and consistency drift you can't catch by eye.
Do roast profiles transfer to a bigger roaster?
Not directly. A profile describes how one machine moves heat into a particular mass of coffee, and a different drum changes the airflow, the thermal mass and how fast the charge takes energy on. Plan to rebuild rather than copy. We develop and prove a profile on the 2 kilo before a production lot goes on the 15 kilo.
Roast a week on somebody else's machine first
If your arithmetic says the week no longer fits, the least committal way to test that conclusion is to roast production somewhere else before you sign for a drum. That's what the Inheritance Coffee Lab in Pensacola is for: hourly access to a 15 kilo production roaster, with a 2 kilo beside it for profile work. The co-roasting application asks four things and takes about five minutes. One caveat worth knowing before you start it: every self-roaster completes the basic roasting class before touching a machine here, with no exemption for experience.
