Truss Method of Joints Calculator

How it is calculated

The tool solves one joint where a vertical load is carried by a single inclined member. Balancing the vertical forces at the pin gives the member's axial force from the angle θ it makes with the horizontal, in degrees:

F = load ÷ sin θ
horizontal component = F × cos θ

The force and its horizontal part are shown as positive magnitudes in newtons, to one decimal. The angle must be above 0° and below 180°; otherwise there is no result. The note depends only on the sign of the load you enter: a positive load is reported as compression, a negative load as tension, and a load of zero as "Zero force". The tool has no idea what the rest of the truss does. Bigger loads and flatter angles give larger forces, since sin θ shrinks toward zero.

Common mistakes

• Measuring the angle from the vertical. The formula uses the angle from the horizontal; typing 60 for a member 30° off the horizontal gives 11,547.0 N instead of 20,000.0 N.
• Using kilonewtons or kilograms. The load is read as newtons and the result is in newtons; a mass in kg must first be multiplied by about 9.81.
• Applying the single-joint result to a joint with two or more unknown members. The tool assumes one inclined member takes the whole vertical load, so it cannot solve a typical interior joint.
• Trusting the Compression or Tension label as a physical finding. It only follows the sign you typed for the load, so a joint that really puts the member in tension needs a negative load to get that label.
• Entering very small angles. At 1° the member force is over 57 times the load (572,986.9 N for 10,000 N), which is correct maths but a sign the geometry is unrealistic.