How Many 1020 Trays Fit on a Greenhouse Bench? Plan Depth, Width
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The number of 1020 trays on a bench comes down to two measurements: how deep the bench is and how long it is. One wholesaler lists a 1020 propagation tray at 11 by 22 inches and about 2.5 inches deep, though makers differ. Using that size, a 24-inch-deep, 96-inch-long bench holds about eight trays, while a 33-inch-deep bench holds 12 over the same length.
The "1020" name refers to a nominal 10 by 20 inch flat, but the outside dimension runs larger because of the rim. That gap is why measuring your own tray before buying a bench matters. This guide shows the arithmetic, a table to start from and what to match to the tray.
Start with the real size of your tray
Johnny's Selected Seeds describes the 1020 as "the standard 1020 greenhouse flat". A wholesaler listing for one white propagation tray, with no drainage holes, gives its dimensions as 11 inches by 22 inches by 2.5 inches deep and calls it a greenhouse industry standard size. Treat that as an example, not a promise. Trays from other makers can be slightly longer or wider, and flat rims flare out.
Before you do any bench math, set one of your own trays on a table and measure the outside edge at the rim, since that is where trays touch. Write both numbers down. Everything below uses 11 by 22 inches as the worked example, so redo the sums with your own measurements.
The two ways to lay trays on a bench
You can run the long side of each tray across the bench depth or along the bench length. The count is the same math each way, but different bench depths favor different layouts.
- Long side across the depth. Trays in a single row. Count equals the bench length divided by the tray's short side. This needs a depth of at least 22 inches.
- Long side along the length. Trays in rows. Rows equal the bench depth divided by the short side, and trays per row equal the length divided by 22 inches.
Always round down, because a partial tray does not fit. If you want a small gap between trays for airflow or hand room, add it to each tray dimension before dividing.
Worked table: trays per bench, using an 11 by 22 inch tray
| Bench depth | 48 in. long | 72 in. long | 96 in. long | Layout |
|---|---|---|---|---|
| 14 in. | 2 | 3 | 4 | One row, long side along the bench |
| 18 in. | 2 | 3 | 4 | One row; the extra depth is wasted |
| 24 in. | 4 | 6 | 8 | Two rows, or one row of trays turned |
| 30 in. | 4 | 6 | 8 | Same as 24 in.; the extra depth adds nothing |
| 33 in. | 6 | 9 | 12 | Three rows |
The table shows how depth jumps in steps. Going from 24 to 30 inches adds no trays, while 33 inches adds a third row. If you are building or buying a bench, choose a depth that is a clean multiple of your tray's short side, plus a small allowance, rather than a round number. The numbers assume trays packed edge to edge with no gap, so a gap or a divider will reduce the count at the boundaries.
Reach: the limit on depth
A deeper bench holds more but is harder to work. The University of Georgia hobby greenhouse bulletin says a side bench should be no wider than you can reach across, roughly 2 to 3 feet, and that a center bench reached from both sides could be as wide as 6 feet. It gives a working height of 36 inches.
A 33-inch-deep bench sits inside that 2 to 3 foot range, but the back row is at the far end of your reach. A bench against a wall with only front access, or a short person, may prefer two rows at 24 inches. Our bench top materials post covers surfaces, and our seed-starting bench setup guide covers the heat, light and water equipment that goes with the trays.
Match the gear to the tray
The tray count matters less if the gear above and below it does not fit. Check each of these against the real tray:
- Heat mat. Mats are sold by size. Check the mat's dimensions against the tray footprint, and see our heat mat and thermostat guide.
- Dome or cover. Domes are made for specific tray sizes and heights. Confirm it fits the 1020 you own.
- Insert cells. Cell inserts fit particular trays, so check the maker's listing for the tray size they suit.
- Shelf depth. If shelving depth is only 14 or 18 inches, trays go long side along the shelf and you get one row.
- Light width. A grow light has a coverage area. Check the maker's guidance for the trays it can cover. See our grow light guide.
- Bottom-watering. A solid tray under a cell tray changes the fit. Measure the stack height if you use more than one layer.
1020 propagation trays
Buy a few and measure them before you commit to a bench size. Choose trays with or without drainage holes depending on how you water.
Seedling heat mat sized for a 1020 tray
Heat mats come in sizes for one or two trays. Match the mat to the tray footprint and plan the electrical connection with the mat's instructions.
A quick planning example
Say you expect to hold 12 trays in the busiest week. With the 11 by 22 inch example tray, a 24-inch-deep bench holds eight trays per 96 inches of length, so 12 trays needs about 144 inches, or 12 feet, of bench. A 33-inch-deep bench holds 12 trays in 96 inches, so about 8 feet does the same job.
The deeper bench takes less length but demands more reach. Which is better depends on your wall space and your arms. Sketch both on graph paper at the scale of your greenhouse before choosing.
Plan the bench before you buy it
- Measure your tray at the rim and note the short and long sides.
- Decide how many trays you need at peak, in a typical spring week.
- Choose a depth that fits whole rows and stays inside your reach.
- Divide the available length by the tray width or length, depending on layout, and round down.
- Check that shelves, mats, domes and lights match the tray.
- Compare with the space in the greenhouse. Our post on how big a greenhouse should be helps with the whole floor plan.
Measure your own 1020 tray at the rim, then divide the bench depth and length by the tray sides and round down. Pick a depth that suits whole rows within your reach, and check that the heat mat, dome and light fit the tray before you buy the bench.
Frequently Asked Questions
How big is a 1020 tray?
The name means a nominal 10 by 20 inch flat, but one wholesaler lists an 11 by 22 inch outside size with a depth of 2.5 inches. Makers differ, so measure your own at the rim.
How many 1020 trays fit on a 4-foot bench?
Using an 11 by 22 inch tray, a 24-inch-deep, 48-inch-long bench holds about four, and a 33-inch-deep one about six. Recalculate with your own tray size.
What bench depth is best for 1020 trays?
One that is a clean multiple of the tray side: 24 inches gives two rows of the short side, 33 inches gives three. Keep it within comfortable reach.
Do I need gaps between trays?
Gaps help airflow and handling but reduce the count. Add the gap to each tray dimension before dividing.
How deep should a seed-starting shelf be?
Deep enough for the tray you use. A shelf that is only slightly wider than the short side holds one row, so match it to your trays.
Sources read for this article:
- Eddi's Wholesale, propagation tray 1020 listing: the 11 by 22 by 2.5 inch dimensions used in the worked table, and the description as a greenhouse industry standard size. One maker's tray, used as an example.
- Johnny's Selected Seeds, leakproof 1020 trays: the 1020 as a standard greenhouse flat.
- University of Georgia Extension, Hobby Greenhouses (Bulletin 910): bench reach and working height.
Trays vary by maker, so the table is arithmetic on an example size, not a statement about any particular tray, shelf, mat or light. Check each product's dimensions with the maker.