Laundromat: Dryers Needed for Wash Volume

All versions

Nothing jams a laundromat like too few dryers — wet loads pile on the folding table while customers wait. Match dryers to wash output: loads per hour times the drying minutes, divided by 60, tells you how many machines it takes to keep the floor moving.

Quick formula: Loads per hour times dry minutes, over 60:

=ROUNDUP(B2*C2/60,0)

Twelve wash loads an hour, each needing 45 minutes to dry, calls for 9 dryers to keep pace.

Functions used (tap for the full reference guide):

ROUNDUP

The example

Three stores with different wash throughput and dry times.

	A	B	C	D
1	Store	Loads/hr	Dry min	Dryers
2	Main St	12	45	9
3	Oak Ave	8	40	6
4	Downtown	20	50	17

The formula

Each load ties up a dryer for its dry time, so the dryer-hours per hour is the machine count:

=ROUNDUP(B2*C2/60,0) // loads/hr x dry minutes / 60, rounded up to whole dryers

How it works

Think in dryer-minutes:

B2*C2 is total drying minutes demanded each hour — 12 loads at 45 minutes is 540 dryer-minutes.
/60 converts that to dryer-hours per hour, which is exactly the number of machines running continuously.
ROUNDUP(...,0) rounds up, because you cannot install a fraction of a dryer and expect it to keep up.
The result is the minimum to break even with wash output; a busy store wants a machine or two of headroom.

The classic rule of thumb is roughly two dryers per washer, and this formula is why: a wash cycle is shorter than the drying that follows, so dryers have to outnumber washers to avoid a pileup.

Try it: interactive demo

Interactive

Enter the wash loads finishing per hour and the average dry time.

Wash loads per hour

Dry minutes per load

Variations

Add headroom

Pad the count for peak times and machines out of service.

=ROUNDUP(B2*C2/60*1.2,0)

Dryers per washer

Compare the result to your washer count for the equipment ratio.

=ROUNDUP(B2*C2/60,0)/E2

Pitfalls & errors

Use realistic dry times. A single-load dryer running heavy items can take an hour, and undercounting the minutes leaves you short of machines exactly when the store is busiest.

Big double- and triple-load dryers change the math — one can clear two wash loads at once. Adjust the dry-minutes figure to reflect the loads a machine actually handles.

Practice workbook

📊

Download the free Laundromat: Dryers Needed for Wash Volume practice workbook

Edit the yellow loads-per-hour and dry-minute cells; the dryer count recalculates.

Frequently asked questions

Why do dryers outnumber washers?

A wash cycle usually runs 25 to 35 minutes, but drying takes 40 to 60. Since each load spends longer in a dryer than in a washer, you need more dryers to keep wet loads from backing up — often about two to one.

Does this size the washers too?

No — it sizes dryers against a wash output you already have. To size washers, work from customer demand per hour and the wash cycle time, then use this formula to match dryers to that output.

Stop fighting formulas. Learn them in a day.

This recipe is one of hundreds of real-world formulas we teach. Our Excel Formulas & Functions class covers lookups, logic, text, and dynamic arrays hands-on — live in Dallas–Fort Worth, Houston, Austin, Oklahoma City, Denver, or online.

See the Formulas & Functions Class

Function references: ROUNDUP