Help and support

1. Open the calculator and choose New model (or start from a worked example).
2. Enter the span, then the supports, loads and the section. The beam wizard walks you through each.
3. Press Ctrl+Enter or choose Analyze, then open Results to see reactions and diagrams.

For a guided tour with pictures, see How it works.

Your model is autosaved in this browser (local storage) and is never uploaded. To keep it elsewhere, save it as a JSON file or copy a share link, which carries the model inside the URL. Clearing your browser data removes the autosave.

The built-in examples are textbook-style problems with hand-calculated answers shown next to the computed ones. Browse them on the examples page.

Open Units in the calculator and pick SI, MKS or US, or set a custom unit for each quantity (length, force, moment, stress and so on). All values are stored in SI internally, so changing units only changes how numbers are displayed and entered; it never changes the result.

Yes. Fields accept expressions such as L/3 and unit suffixes such as 12 kN. A number without a unit is read in the current display unit.

Axial force is positive in tension. Bending moment is positive when it causes sagging in a horizontal member, and shear is defined by V = dM/dx, so a simply supported beam under gravity has positive shear at its left end. Gravity acts in the −Y direction, and rotations follow the right-hand rule (counter-clockwise in 2D). The full definitions are in the theory notes.

The model has no stiffness against some movement, so it could move freely like a mechanism. The message names the node and the direction. Check these in order:

1. Are there enough supports to stop rigid-body movement? A 2D structure needs at least three independent restraints, and a 3D structure at least six.
2. Have you released too many member ends or placed hinges so that part of the structure can swing?
3. Are all members connected to nodes that belong to the structure (no loose or duplicate nodes)?
4. In a 2D truss, every node needs members in at least two directions.

Check the units of every input, the section and material properties (E, I, A), the direction and sign of loads, and which support types you chose. Compare against a quick hand calculation: a simply supported beam under a uniform load w should give R = wL/2 and M_max = wL²/8.

You can model a structure, run the analysis and see the shape of the shear and moment diagrams without an account. The numeric values (reactions, diagram values, result tables), 3D results, the step-by-step report, code export and load combinations need a Student or Pro plan, which you can try free for 3 days (see pricing). See the privacy page for what is stored.

Ask through the contact page, using the e-mail address you signed in with, and the account data will be removed.

Student and Pro start with a 3-day free trial. You add a card at checkout and nothing is charged during the trial. When it ends, the plan you chose is charged automatically, unless you cancel before then. There is one free trial per account. See how the trial works.

Sign in, open the pricing page and choose Manage subscription on your plan. Cancelling during the trial costs nothing. Later, you keep access until the end of the period you have paid for and are not billed again.

Use Manage subscription, or write to us through the contact page with the topic Billing question and say which plan you want.

The first payment of a yearly plan, and a Lifetime purchase, are refunded in full on request within 14 days of the charge. Monthly renewals are not refundable. See the refund policy, then use the contact page and include your order id.

Dodo Payments e-mails a receipt for every payment. Invoices are also available under Manage subscription on the pricing page. If you cannot find one, ask us with the topic Billing question.

Reload the calculator and sign in again, because the plan is read when you sign in. If a renewal payment failed, update your card under Manage subscription. If it still looks wrong, write to us with the e-mail address of your account and the order id.

Pro or Lifetime. Free and Student are for non-commercial use (study, teaching, research and personal projects).

Open the Report step, choose a level of detail (summary, standard or full) and use Print, then pick “Save as PDF” in your browser’s print dialog. The report can also be downloaded as HTML or LaTeX.

Open the Code step and choose Python (NumPy) or MATLAB/Octave. The script is self-contained and reproduces the analysis of your model on your own computer.

Any current version of Chrome, Edge, Firefox or Safari. The app uses ES modules and needs JavaScript. The 3D viewer and the in-browser Python option load extra libraries from a content delivery network, so they need an internet connection the first time. On phones the calculator works in a compact layout, but a larger screen is more comfortable for editing models.