Plant Design

Capacity Sizing for a Commercial Laundry Plant: The Calculation Method

Getting the installed capacity of a new laundry plant right is one of the most consequential decisions in plant design. Undersized plants create operational backlogs that cannot be resolved without capital expenditure; oversized plants consume more capital than necessary and run at low utilisation. The calculation method is straightforward if the inputs are accurate.

Published December 20, 2025 — Stalwart Engineering Technical Notes

The first step in sizing a laundry plant is establishing the daily linen weight to be processed — the gross weight of soiled linen entering the plant each day, expressed in kilograms. This figure is not the same as the number of rooms in a hotel or the number of beds in a hospital, and that distinction matters.

Calculating daily linen weight

For a hotel laundry, the daily linen weight is the product of the linen par stock (the number of changes per item per day multiplied by the number of occupied units) and the weight per item. A typical 200-room hotel with 65 percent average occupancy processes approximately 400 to 600 kg of linen and towels per day, plus 50 to 150 kg of food and beverage linen (napkins, tablecloths), plus 30 to 60 kg of staff uniforms. Total: 480 to 810 kg/day for the operational baseline.

For a hospital laundry, the calculation is based on linen consumption per occupied bed per day, which varies by ward type: general wards generate approximately 3 to 4 kg of soiled linen per bed per day; surgical wards generate 5 to 8 kg; intensive care units generate 8 to 14 kg due to high turnover of sterile drapes and linen. A 300-bed hospital with a mixed case mix typically generates 1,000 to 1,500 kg of soiled linen per day.

Converting daily weight to required throughput

Daily linen weight must be converted to hourly throughput to size the washing equipment. The conversion depends on two parameters: the number of operating hours per day, and the machine utilisation factor.

Operating hours per day: A laundry running a single eight-hour shift processes linen for a maximum of seven effective hours per shift after accounting for shift start and end procedures, machine cleaning, and break time. A two-shift operation provides 14 effective hours. Some healthcare laundries operate 20 or 24 hours per day for continuous throughput.

Machine utilisation factor: No machine runs at 100 percent of rated capacity continuously. Loading, program selection, unloading, and brief idle periods between loads reduce actual throughput to typically 70 to 80 percent of the theoretical maximum (the rate calculated by dividing drum capacity by total cycle time). A utilisation factor of 0.75 is the standard planning value for a reasonably well-managed laundry.

The formula for required installed washing capacity (in kg per hour) is:

Required capacity = Daily linen weight ÷ (Operating hours × Utilisation factor)

For a 500 kg/day hotel laundry running a single eight-hour shift: 500 ÷ (7 × 0.75) = 500 ÷ 5.25 = 95 kg/hour required throughput.

Translating throughput to machine specification

With the required throughput established, the next step is to select a machine configuration that delivers it. Machine throughput is calculated from drum capacity divided by total cycle time (in hours). A 50 kg machine running a 45-minute cycle delivers 50 ÷ 0.75 = 67 kg/hour. Two such machines running simultaneously deliver 134 kg/hour.

For the 95 kg/hour requirement in the example above, options include: one 100 kg machine running a 60-minute cycle (100 kg/hour); or two 50 kg machines running 45-minute cycles (134 kg/hour). The two-machine option provides redundancy — if one machine is out of service, the plant can still process at 67 kg/hour — and more scheduling flexibility for mixed linen types.

Planning headroom and future capacity

The calculated required capacity is a minimum, not a target. Standard practice is to install at least 20 to 25 percent more capacity than the calculated requirement. This headroom accommodates: peak days (public holidays, full occupancy weekends in hotels) when linen generation exceeds the daily average by 20 to 30 percent; maintenance downtime on one machine; and the operational reality that new plants typically experience higher demand than initially projected as the facility grows its utilisation.

A hotel planning for 200 rooms at 65 percent occupancy should size the laundry for 85 percent occupancy with 20 percent headroom, even if occupancy at opening is lower. The additional capital cost of a marginally larger machine at the time of installation is far less than the cost of adding a new machine later, including the downtime for installation and commissioning.

Matching washing capacity to downstream equipment

A common planning error is sizing the washing capacity correctly but undersizing the extraction and drying capacity that follows it. The drying tumbler is the bottleneck in most laundry plants because drying takes longer than washing for most fabric types. A good rule of thumb is to size the total drying capacity at 1.5 to 2 times the total washing capacity, to ensure that wet linen from the washer-extractors does not accumulate waiting for a drying tumbler to become available. Similarly, the hydro extractor capacity (if standalone extractors are used rather than washer-extractors with integrated extraction) must match the washing throughput without creating a queue of wet loads.