Step-by-Step Guide to Computing Machine Hour Rate

A factory running ten different machines rarely has ten identical cost structures. Some machines guzzle power, others need constant maintenance, and a few sit idle between jobs. The machine hour rate method exists precisely to solve this problem: it lets a cost accountant work out exactly how much overhead one hour of running a specific machine should carry. Getting this computation right is one of the more practical skills in cost accounting, and once you break it into steps, it stops feeling intimidating.

What exactly is the machine hour rate? 🔗

The machine hour rate is the hourly cost, in terms of factory overheads, of operating a particular machine. It is found by taking the overheads linked to that machine over a period and dividing them by the hours the machine actually worked. This is essentially an overhead absorption rate, similar in spirit to a direct labour hour rate, except the machine rather than the worker becomes the basis for charging overheads to production.

This method matters most in capital-intensive setups where machines, not people, drive output. In such factories, most overheads such as power, depreciation, and maintenance stem directly from machine operations, so basing overhead absorption on machine hours gives a fairer, more accurate picture than using labour hours or units produced.

Step 1: Treat each machine as a separate cost centre 🔗

The computation starts by treating each machine, or a group of similar machines, as its own smaller department within the larger production department. This is the same logic used in departmentalization of overheads, where a factory is divided into cost centres so that expenses can be traced and charged accurately. Once every machine has its own identity as a cost centre, all overheads connected with it can be pinned down instead of being buried inside one large factory-wide overhead figure.

Step 2: Allocate and apportion overheads to the machine 🔗

With cost centres defined, the next task is distributing overheads across them. This happens in two ways.

Allocation 🔗

Allocation applies when an expense can be traced wholly and directly to one machine, such as the depreciation on that specific machine or the wages of an operator dedicated to it. The full amount goes straight to that cost centre.

Apportionment 🔗

Apportionment is used when a cost is shared across several machines or departments and cannot be assigned to just one. The Chartered Institute of Management Accountants defines apportionment as sharing costs among cost centres in proportion to the estimated benefit received, using a reasonable basis such as floor space, horsepower, or value of machinery. Factory rent, for instance, might be apportioned on floor area, while insurance on machinery is apportioned according to the value of each machine.

Together, this process of allocating and apportioning overheads to cost centres forms what accountants call the primary distribution of overheads, and it is the same first stage described in broader frameworks of overhead allocation, apportionment, and absorption, where costs move from being collected in general to being assigned specifically before finally being absorbed into products.

Step 3: Split overheads into fixed and variable categories 🔗

Once overheads are traced to a machine, they need to be separated into two buckets, because the two behave very differently and are eventually converted into two separate hourly rates.

Fixed overheads (standing charges) 🔗

These are expenses that stay the same regardless of how much the machine runs. Examples of standing charges include rent and rates, lighting and heating, insurance, and supervisory labour attached to the machine or department. Whether the machine runs for 100 hours or 1,000 hours in a month, these costs do not change.

Variable overheads (machine expenses) 🔗

These costs rise and fall with actual machine usage. Depreciation, repairs, power consumption, and lubricants are treated as variable, or machine, expenses because they are directly tied to running hours. Some accountants classify depreciation as fixed depending on the method used to calculate it, but for machine hour rate purposes it is conventionally treated as a variable expense since higher usage typically means faster wear.

Step 4: Work out effective machine hours 🔗

Before dividing costs by hours, you need a realistic figure for how many hours the machine will actually run. This is not simply the total available hours in a year. Budgeted working hours are typically calculated on the basis of hours per day across the working days in a year, then reduced for time lost to plant maintenance and machine setup. What remains after subtracting this idle or setup time is the effective, or normal, working hours of the machine.

Using effective hours rather than total available hours matters a great deal. If a factory ignores idle time and divides overheads by the full theoretical hours, the resulting rate looks artificially low, and jobs charged at that rate end up under-recovering their true overhead cost.

Step 5: Calculate the fixed hourly rate and variable hourly rate separately 🔗

With overheads classified and effective hours determined, two separate rates are computed:

Keeping these separate, rather than lumping all overheads together, is what makes the machine hour rate a more precise tool. It allows a business to see exactly how much of the hourly cost is unavoidable regardless of usage and how much scales with actual production.

Step 6: Add the two rates to get the total machine hour rate 🔗

The final machine hour rate is simply:

Machine hour rate = Fixed hourly rate + Variable hourly rate

To put numbers to it, consider a simplified illustration. Suppose a machine has standing charges of ₹35,000 a year and machine expenses of ₹52,500 a year, and its effective working hours for the year come to 2,500 hours after deducting idle and setup time.

This ₹35 per hour becomes the rate at which overhead is charged to every job or product based on the number of hours that machine spends on it. This mirrors how a predetermined absorption rate is applied to products using historical overhead and hour data, with any difference between overhead absorbed and overhead actually incurred showing up as under- or over-absorption once actual figures come in.

Why this level of detail matters 🔗

It might seem like overkill to separate fixed and variable overheads instead of computing one blended rate. But the split has real value. If a machine sits idle for part of the year, the fixed portion of overheads still needs to be recovered, and knowing the fixed rate separately helps management measure the cost of that idle time. It also helps in decisions like whether to run a machine for overtime production, since only the variable rate needs to be considered for that incremental hour, not the fixed portion which is already committed.

The method does come with a practical cost: under-absorption or over-absorption arises whenever actual overheads or actual hours differ from what was budgeted, so businesses using this approach need to track machine hours diligently and revise rates periodically. This additional clerical effort is why the method suits machine-intensive industries far better than labour-intensive ones, where a simpler labour hour rate may be adequate.

Putting the steps together 🔗

To recap the full computation in sequence: treat each machine as a cost centre, allocate and apportion overheads to it through primary distribution, split those overheads into fixed standing charges and variable machine expenses, determine effective machine hours after removing idle and setup time, compute the fixed and variable hourly rates separately, and finally add them to arrive at the total machine hour rate. Each step feeds directly into the next, which is why skipping the classification or the effective-hours adjustment throws off the final rate.

What do you think? If a machine in a factory frequently breaks down and needs unplanned repairs, how do you think that should affect its machine hour rate calculation? And between a blanket rate for an entire factory versus a separate rate for each machine, which approach would you trust more for pricing a customised, machine-intensive order?

References

1. https://www.financestrategists.com/accounting/cost-accounting/overhead-costing/computation-of-machine-hour-rate/
2. https://www.financestrategists.com/accounting/cost-accounting/overhead-costing/departmentalization-of-overheads/
3. https://www.vskills.in/certification/tutorial/apportionment-of-overheads/
4. https://accountingbody.com/articles/overheads-allocation-apportionment-and-absorption
5. https://www.yourarticlelibrary.com/cost-accounting/machine-hour-rate/machine-hour-rate-calculation-advantages-and-disadvantages/55664
6. https://www.accountingtools.com/articles/what-is-the-rate-of-absorption-in-accounting.html
7. https://icmai-blob.demoapplication.in/Upload/students/P8_0904_2026.pdf