Body Tube Size Chart — RocketMaterials.org article title card
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Body Tube Size Chart: Standard Dimensions

ByBen Shannon

Correction: An earlier version of this chart gave incorrect BT-70 and BT-80 diameters and treated airframe diameter as a motor-size limit. This version uses published supplier dimensions. Measure the actual tube and matching part before gluing: nominal labels are not a fit guarantee.

Model rocket body tube size chart

These are the outside diameter (OD), inside diameter (ID), and wall thickness of standard thin-wall paper tubes listed by eRockets. The metric figures are conversions rounded to 0.1 mm, not separate product specifications.

Tube OD (in) ID (in) Wall (in) OD (mm, approx.) ID (mm, approx.)
BT-5 0.541 0.515 0.013 13.7 13.1
BT-20 0.736 0.710 0.013 18.7 18.0
BT-50 0.976 0.950 0.013 24.8 24.1
BT-55 1.325 1.283 0.021 33.7 32.6
BT-60 1.640 1.600 0.021 41.7 40.6
BT-70 2.217 2.175 0.021 56.3 55.2
BT-80 2.600 2.558 0.021 66.0 65.0

Check the supplier’s listing for the exact tube you buy. Heavy-wall tubes and similarly named products have different dimensions. For example, eRockets lists BT-80H at 2.635 inches OD, not 2.600. Apogee’s standard BT-80 independently lists 2.600 inches OD and 2.558 inches ID.

Choose parts by the surface that fits

A nose-cone shoulder and a tube coupler fit inside the body tube, so compare their outside diameter with the tube’s ID. A sleeve that slides over a tube needs its ID compared with the tube’s OD. Leave room for finish, glue, and manufacturing tolerance. A snug dry fit is more useful than assuming that two parts marked “BT-60” are interchangeable.

Tube size alone does not determine which motor class a rocket can fly. An 18 mm motor commonly uses a BT-20-size motor tube and a 24 mm motor a BT-50-size motor tube, but the motor mount can sit inside a larger airframe. The finished rocket still needs a suitable mount, stability, recovery system, and a motor within its designed limits. Apogee’s tube-size overview is a useful cross-check for nominal size families.

Paper, phenolic, or fiberglass?

This table covers standard paper tubes. A fiberglass or phenolic tube with the same nominal diameter may have a different wall thickness and ID; do not use the paper-tube ID to order its coupler or nose cone. Compare the maker’s actual specification. See the cardboard and fiberglass comparison and the phenolic and fiberglass comparison for material trade-offs.

Before you order

  1. Write down the tube maker, product line, OD, ID, and wall thickness.
  2. Check the nose-cone shoulder or coupler specification against that exact ID.
  3. For a motor mount, check motor diameter, mount-tube dimensions, and centering-ring fit separately.
  4. Test-fit parts before adding glue or paint. If the catalog gives only a nominal size, ask the supplier for measured dimensions.

Dimensions: eRockets body tube size table, cross-checked against Apogee’s nominal sizing guide and its BT-80 product specification. Supplier measurements may vary by product and production run.

For more help choosing a tube, explore the body-tube materials, fit and cost guides.

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