Free Truss Calculator / Roof Rafter Calculator

Calculate the Axial forces for Truss, Roof and Rafters

About this Truss Calculator

This free online truss calculator is a truss design tool that generates the axial forces, reactions of completely customisable 2D truss structures or rafters. It has a wide range of applications including being used as a wood truss calculator, roof truss calculator, roof rafter calculator, scissor truss calculator or roof framing. Trusses are typically modelled in triangular shapes built up of diagonal members, verical members and horizontal members.

How to use this Rafter Calculator?

Simply add nodes, members and supports to set up your model, apply up to 5-point loads (distributed loads can be added in full version), then click solve to run the static 2D truss analysis. It is particularly useful as a steel bridge truss design software or roof truss calculator. Click 'Reactions' or 'Axial Force' to display your results in a nice, clean and easy-to-interpret graph for your truss design. Users can also control settings such as units, display settings of truss members etc. by clicking the 'Settings' button.

This rafter truss calculator, has a range of applications including being used as a wood truss calculator, roof truss calculator, roof rafter calculator, scissor truss calculator or for roof framing. By upgrading to on of SkyCiv's pricing options, you'll have access to full structural analysis software so you select materials such as wood and steel to perform truss designs - making it much more than a simple roof calculator.

Need More Functionality?

Upgrade to a professional plan to unlock full features

Hand Calculations

SkyCiv shows the step by step calculations for how to calculate a truss and the axial forces using method of joints. Upgrade to a paid plan to view these interactive hand calculations.

Unlimited Loads & Supports

Add as many supports, loads, and members with on of SkyCiv paid plans. Tackle any truss designs with this powerful and fast truss software.

Truss Design Software

Run design checks on your trusses as per AISC, NDS, Australian Standards, CSA and Eurocode. Simply model your truss structure and run beam design checks as you need them.

Learn More Upgrade Now!

Rafter Calculator

Whether you call them rafters, truss members or beams - the truss calculator essentially does the same thing. It calculates the internal axial forces in these members. The internal forces are important as they are commonly the governing force to look for in truss structures. Such structures are frequently used in long span structures such as truss bridge design and roof trusses.

Truss Solver

The truss analysis is being performed by our FEA solver, which is also used in our Structural 3D program. The calculations made are based on splitting the member into 10 smaller elements and calculating the internal forces based on these. The Truss solver can handle extremely large structures of more than 10,000 members. So if you have a larger structure, simply upgrade and you can use the full S3D program for all your analysis needs.

More Information on Trusses

A truss is typically a triangular structure that is connected by pinned joints such that they mainly incur an axial force (see what is a truss). This above tool will allow you to run truss analysis on any of these trusses to get the internal member forces. There are a number of different types of trusses, including pratt truss, warren truss and howe truss; each with their own set of pros and cons.

Do More With Structural 3D

There are some limitations on the above truss calculator that can be achieved through full structural analysis software. Get more results (such as bending moment and shear force diagrams), get more members and loading types (area loads, distributed loads and self weight) and model in 3D.

About SkyCiv

SkyCiv offers a wide range of Cloud Structural Analysis and Design Software for engineers. As a constantly evolving tech company, we're committed to innovating and challenging existing workflows to save engineers time in their work processes and designs.

If you are an engineering professional, you might benefit more by using our cloud based 3D Structural Analysis Software beyond this calculator. This software includes integrated design modules such as AISC, ACI, AS, Eurocode and CSA. Check out our professional packages here:

3D Structural Analysis Software

Responses (45)

  1. Peter Dow
    March 27, 2018 at 5:26 am · Reply

    Hi I have just signed up for your free online truss calculator. I want to input this image (or indeed any image) to your program so I can use my image as a background so that I can quickly input the nodes using my mouse.
    This is the pedestrian bridge which collapsed recently in Florida.

    Alternatively can you model this and add it to your examples?

    • Joe Anderson
      August 9, 2018 at 9:17 am · Reply

      If that is your plan, you are just wasting your time. Engineering by sheer laziness is probably how the bridge collapsed in the first place.

      • Paul
        August 9, 2018 at 2:01 pm · Reply

        It might be a handy feature to insert the nodes of the structure in roughly the correct position. After insertion the user could then edit the node position correctly. If it interests anyone we did have a few users model this structure after the collapse. An example is below:

        • Peter Dow
          August 9, 2018 at 7:10 pm · Reply

          Thanks again Paul. Your help was invaluable.

      • Peter Dow
        August 9, 2018 at 7:10 pm · Reply

        A lot has happened in the 4 months since I posted that.
        I signed up for a free account with SkyCiv to model that truss.
        My model had 13 nodes and 23 members (which is more than the free account can cope with) but no worries because I wrote to SkyCiv and Paul was kind enough to give me a 14 day free trial of the entire SkyCiv suite, which I put to very good use – and could not have analysed this structure without such a modelling tool – so not “wasting my time at all”.
        We’ve discussed this on some science and engineering forum topics, if you are interested?

        • Joe Anderson
          August 23, 2018 at 5:33 am · Reply

          “and could not have analysed this structure without such a modelling tool”

          I’m guessing you aren’t an engineer. Software like this is just a tool, and you should not be using it if you don’t understand the engineering theory behind it. Traditionally a problem like this it would be done with method of joints in conjunction with a linear equation solver. There is nothing wrong with using software like this, but you are going down a very dangerous road if you are relying on it with minimal engineering knowledge. Also, in my opinion quick inputs with a mouse is great for Photoshop, but such methods have no business in engineering applications.

          • bob
            September 10, 2018 at 4:32 pm ·

            @disqus_VlwAvk0a3L:disqus I think you might need to get a life and stop being a little bit of a pain. You don’t know why he’s using it so maybe just back out.

  2. […] Данный сервис расположен по адресу — […]

  3. Donovan Jones
    October 24, 2017 at 1:27 pm · Reply

    I cannot seem to solve the truss, because it is asking to specify the material for section 1. How do I do this?

    • Paul
      October 24, 2017 at 1:31 pm · Reply

      Hi there. It shouldn’t be required to enter a material but something could be going wrong for you. Could you please share the truss with me (take a screenshot and post here or send to [email protected] ) so we can get to the bottom of this for you?


      • Alabaster Acres
        February 10, 2018 at 1:57 pm · Reply

        I am having the same issue

        • Paul
          February 10, 2018 at 3:17 pm · Reply

          Could you please share the truss with me (take a screenshot and post
          here or send to [email protected] ) so we can get to the bottom of this
          for you?

      • Jacob Drescher
        February 10, 2018 at 2:45 pm · Reply

        I am also having this same issue

        • Paul
          February 10, 2018 at 3:17 pm · Reply

          Could you please do what I said above please? Thanks

          • Jacob Drescher
            February 10, 2018 at 3:22 pm ·

            I actually got it to work. The only difference this time is that I put a 0 for the x reaction instead of leaving it blank when there was only a force along the y axis

  4. Robert Soley
    October 12, 2017 at 6:45 am · Reply

    I can just imagine what kind of tools bought this

    • Paul
      October 12, 2017 at 8:11 am · Reply

      Ummm engineers who need to analyze larger trusses probably…

  5. Charlie
    September 21, 2017 at 8:49 am · Reply

    Paul, I want to add a truss in my garage to hang lighting, pull down air hoses and ceiling fans, etc. I want to use 1 1/8 inch (30mm) square steel tubing which is 3/64 inches (1.2mm) thick to build a truss which is about 40 feet long. The truss will be supported laterally by the same 30mm steel tubing as braces. Can your truss analysis software calculate loads on a steel truss?

    • Paul
      September 21, 2017 at 8:59 am · Reply

      Hey Charlie. Great question! It sounds like an interesting project but you will probably need to use our full 3d structural analysis software for this. It will definitely be able to handle the project. It works almost the same as this truss calculator with all the extra features you will need:

  6. Bryan Groves
    September 14, 2017 at 2:43 am · Reply

    Hi, I was just wondering if there were any capabilities to determine if a truss is internally stable.

    • Paul
      September 21, 2017 at 8:57 am · Reply

      Hi Bryan. We have a new feature called “Truss Hand Calcs”. The check for internal and external stability is performed in the hand calculations we provide.

  7. Neil Chakrabarty
    April 16, 2017 at 1:11 pm · Reply

    Hi Paul, I would like to use your calculator to determine the trusses proposed by my contractor. So can I sign up for a while and stop when the project ends?

    • Paul
      April 16, 2017 at 1:38 pm · Reply

      Hi Neil. Thanks for your question. Yes definitely! One of the great things about SkyCiv is the flexibile subscription. You can cancel your subscription whenever you want without any fees. Simple do this from within your account settings to ensure you do not get billed in your next subscription term. Let us know if you need anything else.

  8. dog
    April 15, 2017 at 10:30 pm · Reply

    take the cost off pissants

  9. Fadhli
    April 14, 2017 at 12:24 am · Reply

    it cant solve because the modulus young’s is zero, can anyone help me where i can put the moudulus youngs data?

    • Paul
      April 14, 2017 at 2:11 pm · Reply

      That’s strange. Young’s modulus shouldn’t be required as it should be entered automatically. Did you end up getting it working? Email me at [email protected] to discuss further if you’re still having issues.

  10. Xander Jake de los Santos
    March 13, 2017 at 8:45 am · Reply

    I also need solutions…
    I have no use of an answer if I don’t know how solve for it…

    • Paul
      April 14, 2017 at 2:11 pm · Reply

      Sorry at the moment we do not have full worked solutions for trusses. You can try it by hand and see if the solution is correct, so it’s not completely usless to you.

  11. Julius Sentirmay
    November 15, 2016 at 4:04 am · Reply

    I installed 18 solar panels on my existing Truss Roof with permit. Now the City asking verification that the roof system can accommodate the additional dead loads of
    the solar equipment. I have the original plan from March 26 2003, and it said the Roof Truss calculation in the City of Meridian. I called the Builder he said the Idaho Truss Company went out from business. I like to calculate the Truss load my self, how can I do it? Our Roof slope 12-8, under the roof we have Bonus room. The roof size 36′ horizontal and 23′ slop size. The Bonus room walls start 10′ from the edges both side, and 6′ height. After this fallow the roof slope 4′. The Bonus room ceiling 10′ wide, it has
    2″x10″ ceiling joints. The 23′ long roof rafters every 3′ distance are supported to Garage ceiling joints. The Garage ceiling joints is 2″x14″ MFG’D Trusses @ 24″ oc. .

  12. Jordan McCallum
    May 21, 2016 at 8:14 am · Reply

    Tell me how many objects I can use in the free trial, getting most-way through a sketchup and be told to pay or quit leaves a very sour taste in the mouth.

    • E-Street Developers
      May 21, 2016 at 9:35 am · Reply

      Hi Jordan,

      I can understand that concern. In the text above the calculator it does mention the limitations of the free software:

      “Please note some features have been disabled and there are limites to what can be added (12 members, 2 supports and 5 point loads only). ”

      Hope this clears up your concern and hope this restores your image of SkyCiv.

  13. […] Free Online Truss Calculator […]

  14. Emad
    February 18, 2016 at 7:08 am · Reply

    I cannot evaluate the SkyCiv truss calculator if I cannot enter node fixities or applied loads. Is there a way to calculate and get results before purchasing?

    • Paul
      February 18, 2016 at 7:18 am · Reply

      Hi Emad. Node Fixities can only be controlled in SkyCiv Structural 3D. I can see you signed up our free account by visiting That’s what I was going to suggest as you can play around with the software more and even give Structural 3D a little trial. This way you can evaluate the software before purchasing. If you have any further questions please email us at [email protected].

  15. Salacorn
    February 16, 2016 at 5:11 pm · Reply

    I always appreciate free trials, especially those that do not require any local installs or regos.

    Whilst I gave this a fair go, I found I was unable to accomplish what I feel is a simple timber truss design on my home. (Fink + King combo). I’m a sparky, certainly not a structural engineer (though my maths and physics are good). I recently bought a home, and upon getting into some renos, noticed some air con tradie cut some web members to run the ductwork years ago. I reckoned it would of been cool to see what effects that might have.

    Either my lack of sleep has gotten to me, or this calculator is not able to have points anywhere but on the ends of a member. This type of truss design seems to fit bridge construction, but in timber trusses for typical buildings, the chords are continuous, with web members between them.

    Again, I could just be too tired and getting it all wrong.

    Either way, it still is a nice tool for other designs.

    • Paul
      February 17, 2016 at 11:08 am · Reply

      Hi Salacorn. Any structure can be entered as you can place the nodes at any position you like. If there is a junction then you need to put a node there and connect the members accordingly. For instance see the structure I’ve attached. You wouldn’t do one of the horizontal member as ONE long member – rather you would break it up as shown so that you can add joints. Hope that helps.

  16. What up tho
    December 8, 2015 at 4:23 pm · Reply

    Can this show how you got the answer

    • Paul
      December 8, 2015 at 4:45 pm · Reply

      Unfortunately no – this can only be done in SkyCiv Beam but even then it will only show the solution for statically determinate problems by method of sections.

      • Swagg
        May 26, 2016 at 12:12 pm · Reply

        Good One Paul

  17. first gear
    November 27, 2015 at 3:18 am · Reply

    please allow me to use 18 members i want to try it before i buy please just want to check if program can solve truss with 18 members

    • Paul
      November 27, 2015 at 8:30 am · Reply

      Hi there. Sorry the free truss calculator is limited and cannot be changed at the moment. Paid SkyCiv Truss can compute up to 30 members while SkyCiv Structural 3D is fully unlimited. Perhaps try SkyCiv Structural 3D as it can be used for FREE for 30 days at the moment. Sign up on the home page. Hope that helps. Contact us at [email protected] if you have any further questions.

  18. Malik Osman
    August 25, 2015 at 8:16 pm · Reply

    invest your time doing a tutorial to use this

    • Paul
      August 25, 2015 at 8:42 pm · Reply

      Hi Malik. Sorry for any inconvenience or frustrations caused by the calculator — Please watch this video from around 2:00 and onwards as it goes through a simple example on how to use the calculator:

      It is for the paid SkyCiv Truss Calculator but it is virtually the same thing with less restrictions. Hope that helps. If you’re still having issues or need some help email us at [email protected] and we’ll do our best to assist you.

  19. Ana
    August 1, 2015 at 2:39 pm · Reply

    Incorrect Reactions, loads are just 15-30kN then Reactions are already millions. :(

    • Paul
      August 1, 2015 at 3:07 pm · Reply

      Hi Ana. Sounds like your structure may not be constrained properly. Could you please attach a screenshot here of your structure so we can see what’s caused this and help you out? Otherwise you can email us at [email protected]. Hope to hear from you soon. Cheers, Paul.

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