To calculate a machine hour rate, add up every annual cost tied to running a piece of equipment and divide by the number of hours the machine actually produces goods during the year. The result is a per-hour overhead figure you can apply to any job based on how long it occupies the machine. The formula itself is simple; the accuracy comes from what you put into each side of it.
Machine Hour Rate = Total Annual Machine Costs ÷ Productive Machine Hours
What Goes Into Total Machine Costs
Every cost that keeps a machine running belongs in the numerator. These fall into two groups: standing charges that stay roughly the same regardless of how much the machine runs, and variable costs that rise and fall with usage.
Standing Charges
Standing charges are the fixed overhead you pay whether the machine runs eight hours or zero. They include the portion of factory rent attributable to the floor space the machine occupies, property taxes on that space, lighting and climate control for the machine area, insurance premiums on the equipment, and supervisor salaries for personnel overseeing operations. The standard approach is to allocate shared costs like rent and utilities based on the square footage each machine occupies relative to the total production floor.
Variable Costs
Variable costs fluctuate with how intensively the machine operates. The biggest line items are usually depreciation, electricity, routine maintenance, and repairs. Power consumption is straightforward when you know the machine’s kilowatt-hour draw: multiply that by your electricity rate for the per-hour power cost. Maintenance and repair figures come from service contracts, historical repair logs, and replacement-part budgets. Consumables like cutting fluids, lubricants, and tooling wear belong here too, though shops sometimes overlook them.
Depreciation deserves its own decision, because it often represents the single largest cost component for expensive equipment and the method you choose can dramatically change your rate.
Choosing a Depreciation Method for the Rate
The annual depreciation figure you plug into the numerator depends on which method you use, and the tax method your accountant uses is usually the wrong choice for internal costing.
Straight-Line
Straight-line depreciation divides the equipment’s cost evenly across its useful life. A $200,000 machine with a ten-year life produces a flat $20,000 charge every year. This creates a stable, predictable machine hour rate and works well for internal cost management when you want consistency across periods.
MACRS, Section 179, and Bonus Depreciation
For tax purposes, most businesses use the Modified Accelerated Cost Recovery System, which front-loads depreciation into the early years. Under MACRS, the default method for most personal property is 200-percent declining balance, switching to straight-line when that produces a larger deduction, and salvage value is treated as zero.1Office of the Law Revision Counsel. 26 USC 168 – Accelerated Cost Recovery System Most manufacturing machinery falls into the seven-year property class, though some equipment qualifies for five- or ten-year recovery.2Internal Revenue Service. Publication 946 (2025), How To Depreciate Property
Two provisions push expensing even faster. Section 179 lets you deduct the full purchase price of qualifying equipment in the year it’s placed in service, up to an inflation-adjusted dollar limit.3Office of the Law Revision Counsel. 26 USC 179 – Election to Expense Certain Depreciable Business Assets Bonus depreciation is a separate path: under legislation signed in 2025, qualified property acquired after January 19, 2025 is eligible for a permanent 100-percent first-year deduction.4Internal Revenue Service. Treasury, IRS Issue Guidance on the Additional First Year Depreciation Deduction Amended as Part of the One, Big, Beautiful Bill
Here is why this matters for your machine hour rate. If you expense a $500,000 machine entirely in year one using Section 179 or bonus depreciation, the depreciation component of the rate is enormous that first year and zero after that. For tax reporting, fine. For internal costing, it distorts what the machine actually costs to operate. Most cost accountants use straight-line depreciation for internal machine hour rates even when the tax return uses MACRS or immediate expensing, specifically to avoid this distortion.
Calculating Productive Hours
The denominator is the hours the machine will actually produce goods during the period. Getting this number wrong, usually by overestimating, is the most common way to end up with a rate that under-allocates overhead and makes jobs look more profitable than they are.
Start with the total hours the factory operates. A single-shift operation running five days a week gives you roughly 2,080 hours per year. Two shifts doubles that to around 4,160. From that starting point, subtract every category of downtime:
- Scheduled maintenance: planned shutdowns for preventive maintenance, calibration, and inspections.
- Setup time: hours spent reconfiguring the machine between production runs, when no sellable goods are produced.
- Anticipated breakdowns: a realistic allowance for unplanned failures, based on the machine’s history.
- Idle time: gaps caused by material shortages, scheduling delays, or labor unavailability.
What remains is your productive hours. A machine with 2,080 theoretical hours might realistically produce goods for only 1,700 to 1,800 hours once you account for everything above.
One more constraint. Under U.S. GAAP, fixed manufacturing overhead should be allocated based on normal capacity, meaning the average production level you expect over multiple periods including routine downtime, rather than actual output in any single period. Overhead that goes unabsorbed because production dipped below normal capacity gets expensed in the current period rather than loaded onto inventory. Build your rate around a normal-capacity hour figure, not an optimistic theoretical maximum.
A Worked Example
Suppose you’re setting the rate for a CNC milling machine. The annual costs break down like this:
- Depreciation, straight-line: $28,000
- Allocated rent and utilities: $6,000
- Insurance: $2,400
- Maintenance and repairs: $5,500
- Power consumption: $4,800
- Consumables and tooling: $3,300
Total annual costs: $50,000. The machine operates on a single shift with 2,080 theoretical hours. After subtracting 180 hours for maintenance, 60 hours for anticipated breakdowns, and 140 hours for setup and idle time, you have 1,700 productive hours.
$50,000 ÷ 1,700 = $29.41 per machine hour.
A job that occupies this machine for six hours absorbs $176.46 in overhead. A twelve-hour job absorbs $352.92. Longer jobs carry a proportionally larger share of the equipment’s operating costs, which is the whole point of using machine time as the allocation base.
One Rate for the Plant or One Per Machine
You can calculate a single composite rate for the entire factory or separate rates for each machine. The right answer depends on how different your machines are.
A plantwide rate lumps all machine-related overhead together and divides by total productive hours across the factory. It’s simple. The problem is accuracy: if your shop has a $1.2 million laser cutter next to a $40,000 drill press, a blended rate overcharges jobs that only use the drill press and undercharges jobs on the laser. That skews pricing decisions.
Individual machine rates take more effort to set up because you track costs and hours for each machine separately, but they produce a far more accurate picture. In shops where equipment varies significantly in value, power draw, or maintenance needs, the improvement in pricing accuracy usually justifies the added bookkeeping.
A middle path that works well for many operations is calculating rates at the department or work-center level, grouping machines with similar cost profiles and assigning a single rate to each group. You capture most of the accuracy benefit without tracking every machine individually.
Reconciling the Rate With Actual Results
Machine hour rates are set at the start of a period using estimated costs and projected hours. Actual results almost never match. The gap between overhead applied to jobs and actual overhead incurred is called a variance, and it has to be cleared at the end of the period.
When actual costs exceed applied overhead, you have underapplied overhead. When applied exceeds actual, overapplied. Either way, the Factory Overhead account needs to be zeroed out because it’s a clearing account, not a permanent balance.
The simplest approach transfers the entire variance into Cost of Goods Sold. Underapplied by $8,000? Increase COGS by that amount. Overapplied by $5,000? Decrease it. This works fine when the variance is small.
For larger variances, a more precise method spreads the difference proportionally across Work in Process, Finished Goods, and Cost of Goods Sold based on the overhead balances in each account. This avoids dumping a large adjustment into one line item and gives a more accurate picture of inventory values.
Persistent variances in the same direction signal that your rate needs updating. If you’re consistently underapplying overhead, either your cost estimates are too low or your productive-hour estimates are too high. Recalculating annually, or mid-year for large swings, keeps job costing reliable.
When This Method Fits Your Operation
Machine hour rates work best in capital-intensive environments where equipment drives the pace of production and represents the dominant cost. Automotive manufacturing, chemical processing, semiconductor fabrication, plastics molding, and CNC machining all fit this profile. Depreciation, power, and maintenance dwarf labor costs, so machine time is the natural allocation base.
The method loses its edge in labor-intensive operations where workers control the speed and quality of output. A custom furniture shop with inexpensive power tools and skilled craftspeople would allocate overhead more accurately using direct labor hours. Pick whichever resource most closely drives your overhead costs. If your operation is a mix, use different allocation bases for different departments rather than forcing one method across the whole business.