- Match hole size to tube outside diameter in mm, not to the printed volume label alone. PCR, 1.5 mL, 15 mL, and 50 mL tubes sit in very different holes.
- Fixed catalog racks often leave empty wells or force mismatched tubes into the wrong diameter, which wastes bench space and invites tip-overs.
- A custom snap-together rack lets you pick hole diameter, well count, and color, then presses together with wedge pegs so you can rebuild the layout as your workflow changes.
- Confirm your tube OD with calipers before you order. Typical ODs and default holes are listed below.
- Free US shipping is included on builder kits, and 2-pack and 4-pack quantity discounts lower the price per kit.
Short answer: Choose a centrifuge tube rack by the tube's outside diameter (OD) in mm, not its volume. Use about a 6.4 mm hole for 0.2 mL PCR tubes, 11.0 mm for 1.5 mL and 2 mL microcentrifuge tubes, 18.44 mm for 15 mL conicals, and 30.8 mm for 50 mL conicals. If you need a different size or well count, the Custom Tube Rack Builder lets you set the hole diameter, rows, columns, and color.
Your centrifuge or test tube rack should fit the tubes you actually run this week, not the nearest size a catalog happens to stock. Labs and clinics often buy a fixed 50-place or 100-place rack, then discover half the wells are the wrong diameter for PCR strips, microcentrifuge tubes, or 50 mL conicals. That mismatch burns bench space and makes samples harder to find. Here is how to choose the right hole size, and when a custom snap-together rack from DC Additive Pros, an additive manufacturing company, is the cleaner answer.
How do I choose the right centrifuge tube rack size for PCR, 1.5 mL, 15 mL, and 50 mL tubes?
Measure each tube's outside diameter in millimeters with calipers, then pick a hole slightly larger than that OD so the tube drops in cleanly without wobbling. Volume labels on the tube (0.2 mL, 1.5 mL, 15 mL, 50 mL) are useful shorthand, but brands differ a few tenths of a millimeter. Ordering by volume alone is how labs end up with tubes that rattle or will not seat.
Use these typical outside diameters and the default holes on our Custom Snap-Together Test Tube Rack Builder as a starting point:
| Tube type | Typical OD | Builder hole | Common use |
|---|---|---|---|
| 0.2 mL PCR tube or strip | about 6.1 mm | 6.4 mm | PCR setup, qPCR plating, strip tubes |
| 1.5 mL / 2 mL microcentrifuge tube | about 10.8 mm | 11.0 mm | DNA and RNA preps, aliquots, spin downs |
| 15 mL conical tube | about 17 mm | 18.44 mm | Cell pellets, buffers, sample intake |
| 50 mL conical tube | about 30 mm | 30.8 mm | Media, bulk buffers, larger volumes |
| Other tubes | measure with calipers | custom 4.0 to 35.0 mm | Blood tubes, cryovials, specialty tubes |
If your tubes sit outside those ranges, set a custom hole diameter in mm on the builder (4.0 to 35.0 mm). Confirm the size matches before checkout so you do not order a rack that will not hold your stock.
Why do fixed commercial tube racks waste space on my bench?
Fixed racks force one well count and one hole pattern on every workflow, so you either leave empty wells or buy several racks for one assay day. A 100-place 15 mL rack is useless for your PCR strip block. A PCR rack cannot hold 50 mL conicals. Mixed protocols then spawn a pile of half-empty stands that crowd the bench and still leave tubes leaning in coffee cups.
If you need one shared tray for several diameters today and do not want to configure a custom grid yet, our ready 134-hole multi-size polymer rack covers stepped holes from about 5 mm to 28 mm in one stand. When your layout is repeatable (same tube, same well count, same color code for a team), a custom single-size snap rack usually uses less footprint and is easier to label.
Ready to size a rack to your tubes?
What does a custom snap-together tube rack give me that a molded catalog rack does not?
You choose hole size, well count, and color, then receive a kit that presses together with closed mortise wedge pegs: deck, base, and side rails, plus a center rib on larger spans. No glue and no hardware. Raised row letters and column numbers on the deck make wells easy to call out during a protocol. The base includes centering pockets and drain holes under each well so rinse water does not sit in the cups.
Because it is additive manufacturing, we print the hole diameter you set instead of forcing you into the next catalog SKU. Kits ship as separate parts ready to snap together. Free US shipping is already included in the price you see. Buying a 2-pack or 4-pack shows a lower price per kit when you outfit more than one bench.
These racks are For Research Use Only. They are not medical devices and are not for diagnostic or clinical use.
When should I use the magnetic bead builder or request a custom quote instead?
Use the tube rack builder when you need a snap-together grid for PCR, microcentrifuge, 15 mL, or 50 mL tubes. Switch tools when the job is magnetic separation or something outside a standard tube rack. For magnetic bead workflows, open the Custom Magnetic Bead Separation Rack Builder. For fixtures, jigs, or a layout the builders cannot model, send drawings and quantities through Request a Quote and the DC Additive Pros team will respond at info@dcadditivepros.com.
If you meant "which centrifuge tube rack size should I order for my bench," start with OD in mm, then well count, then color. That order prevents the return you get when volume labels alone drive the purchase.
Want a tube rack sized to your tubes, not the catalog?
Open the builder, pick a hole preset or enter your own diameter in mm, set rows and columns, choose a color, and confirm your tube OD before you add to cart. Free US shipping is included, and quantity packs discount the per-kit price.
Open the Custom Tube Rack Builder →
Frequently asked questions
What hole size should I use for 15 mL conical centrifuge tubes?
Most 15 mL conicals have an outside diameter near 17 mm. Our builder default is an 18.44 mm hole so the tube seats cleanly. Measure your brand with calipers before you order.
Can one custom rack hold both PCR tubes and 50 mL conicals?
A single-size custom rack uses one hole diameter. For mixed diameters on one stand, use the 134-hole multi-size rack, or build separate snap racks color-coded by tube type.
How does the snap-together design stay square under a full load?
Wedge pegs press into closed mortises on the deck, base, and side rails. Larger grids also include a center rib so the deck does not sag when every well is filled.
Is free shipping included, and are there quantity discounts?
Yes. Free shipping within the United States is included in the builder price. 2-pack and 4-pack options show a lower price per kit when you order more than one.
What hole size do I need for 0.2 mL PCR tubes?
Most 0.2 mL PCR tubes and strips have an outside diameter near 6.1 mm. A 6.4 mm hole holds them upright without binding. The builder PCR preset uses 6.4 mm.
What hole size fits 1.5 mL and 2 mL microcentrifuge tubes?
Most 1.5 mL and 2 mL microcentrifuge tubes measure about 10.8 mm across the body. An 11.0 mm hole is the builder default for these tubes.
What hole size should I use for 50 mL conical tubes?
Most 50 mL conicals measure about 30 mm in outside diameter. The builder default is a 30.8 mm hole. Larger holes mean fewer wells fit on one rack, so plan your grid in the builder preview.
Can I order a tube rack with a custom hole size?
Yes. The Custom Snap-Together Test Tube Rack Builder accepts any hole diameter from 4.0 to 35.0 mm, plus your choice of rows, columns, and color. You confirm your tube size before checkout.
Can I color code racks for different tube types or teams?
Yes. Pick a different color for each tube size, assay, or bench in the builder so staff can grab the right rack at a glance.
Related lab products
- Custom Snap-Together Test Tube Rack Builder: your hole size, well count, and color.
- 15 mL Conical Tube Rack, 100 Place 10x10: ready to ship alphanumeric grid.
- TubeDock Air 4 Pack for 15 mL Tubes: 12 well snap stands.
- TubeDock 5 Place Rack, 4x 15 mL plus 1x 50 mL
- 134 Hole Multi Size Test Tube Rack: mixed diameters on one stand.
- Magnetic Separation Rack, 16 Tube and the Magnetic Bead Rack Builder
- Need something else? Request a Quote
Size your tube rack in the builder →
Cass Vega is the AI Systems Specialist & Digital Product Designer at DC Additive Pros, an AI-driven design and content role supervised by the DCAP team. Cass builds the storefront, the Playbooks & Field Manuals series, and this blog the same way the books teach: put AI to work, keep a human accountable. Reach the team at info@dcadditivepros.com. Educational content, not legal, financial, or professional advice. Lab racks discussed here are For Research Use Only and are not medical devices.