Provides users with a mobile approach to calculating capacities for single bolts, nails, lag screws and wood screws per the 2015 NDS. Both lateral (single and double shear) and withdrawal capacities can be determined. Wood-to-wood, wood-to-concrete, and wood-to-steel connections are possible.


Connection capacities are calculated on the basis of design provisions in the 2015 National Design Specification® for Wood Construction (NDS®). The calculated capacities are based on the following assumptions and conditions:

· Bolts and lag screws must meet the requirements of ANSI/ASME B18.2.1, wood screws must meet the requirements of ANSI/ASME B18.6.1, and nails must meet the requirements of ASTM F1667.
· Bolts, lag screws and wood screws must be installed in predrilled lead holes in accordance with the provisions of NDS Chapter 11.
· Bolts, lag screws and wood screws must not be forcibly driven into connection members with a hammer or other impact device.
· The faces of adjacent connection members are brought into contact when fasteners are installed.
· Adequate edge distances, end distances and spacing must be provided for all fasteners to prevent splitting of wood connection members, in accordance with NDS Chapter 11.
· Steel side plates with thickness of ¼ in. or greater must meet the requirements of ASTM A36, and steel side plates with thickness less than ¼ in. must meet the requirements of ASTM A653, Grade 33.
· Concrete connection members must have compressive strength (fc') of at least 2500 psi.
· The on-line Connection Calculator does not specifically address multiple-fastener connections. See NDS Chapters 10-11 and NDS Appendix E for applicable design provisions.
· The on-line Connection Calculator does not address fasteners installed at an angle to grain (e.g., toe-nails). See NDS Chapters 10-11 for applicable design provisions.
· The on-line Connection Calculator does not address fasteners subjected to combined lateral and withdrawal loading. See NDS Chapters 10-11 for applicable design provisions.
· The on-line Connection Calculator does not address connections with gaps or non-structural spacer blocks between members.

The quality of structural wood products and fasteners and the design of load-supporting members and connections shall conform to provisions of the NDS. The on-line Connection Calculator is based on design equations for lateral loading and withdrawal loading specified in NDS Chapters 10 and 11, along with fastener characteristics specified in NDS Appendix L. The NDS Commentary, NDS Appendices I through N, and NDS Chapters 12-13 provide additional guidelines regarding the design of connections in wood structures.

While every effort has been made to insure the accuracy of the information presented, and special effort has been made to assure that the information reflects the state-of-the-art, neither the American Wood Council nor its members assume any responsibility for any particular design prepared from this on-line Connection Calculator. Those using this on-line Connection Calculator assume all liability from its use.

This Connection Calculator is not meant to be a replacement for the NDS and does not encompass all of its design options.

The American Wood Council
On behalf of the industry it represents, AWC is committed to ensuring a resilient, safe and sustainable built environment. To achieve these objectives, AWC contributes to the development of sound public policies, codes and regulations that allow for the appropriate and responsible manufacture and use of wood products. We support the utilization of wood products by developing and disseminating consensus standards, comprehensive technical guidelines and tools for wood design and construction, as well as providing education regarding their application. Contact AWC via email: or connect with one of AWC’s regional building code experts.

What’s New

Version 2.1.51

Additional diagnostics

Ratings and Reviews

Molz14 ,

Great idea, but crashes

This app would be great for a structural engineer like myself. However, after I put in all the info and press calculate, it quits. I haven't seen a solution to my inputs yet. It quits every time. Great idea, just need to fix the crashing.

Robtheengineer ,

Stopped working

Good app, but stopped working with ios 9. Please fix.

App Privacy

The developer, American Wood Council, has not provided details about its privacy practices and handling of data to Apple. For more information, see the developer’s privacy policy.

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The developer will be required to provide privacy details when they submit their next app update.


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