Find sides from right triangles, SAS, perimeter, and angle cases. Export tables, steps, and summaries. View clean results above the form after submission instantly.
| Method | Known Values | Missing Side Result | Notes |
|---|---|---|---|
| Right Triangle | a = 3, b = 4 | c = 5 | Uses the Pythagorean theorem. |
| SAS | a = 7, b = 9, C = 60° | c ≈ 8.185353 | Uses the Law of Cosines. |
| Angle-Side-Angle | a = 10, A = 40°, B = 65° | b ≈ 13.167318 | Uses the Law of Sines. |
| Perimeter Method | a = 6, b = 8, P = 20 | c = 6 | Subtracts known sides from perimeter. |
Use the Pythagorean theorem when the triangle has one right angle.
c = √(a² + b²)
a = √(c² - b²)
b = √(c² - a²)
Use the Law of Cosines when two sides and the included angle are known.
c = √(a² + b² - 2ab cos(C))
Use the Law of Sines when one side and two angles are known.
b = a × sin(B) / sin(A)
Use perimeter subtraction when two sides and the total perimeter are known.
c = P - a - b
This missing triangle side calculator helps you solve unknown lengths with several reliable methods. It works for right triangles, side-angle-side cases, angle-side-angle cases, and perimeter-based problems. That range makes it useful for homework, drafting, design checks, and daily geometry work.
Many triangle tools only cover one formula. This page supports multiple setups on one screen. You can switch methods without leaving the page. The result appears above the form after submission, so the answer is easy to review. The calculator also shows side values, perimeter, area, steps, and a clean graph.
Each method uses a standard geometry rule. Right triangle problems use the Pythagorean theorem. SAS problems use the Law of Cosines. Angle-side-angle problems use the Law of Sines. Perimeter problems subtract the known sides from the full perimeter. The code also checks for impossible inputs. That step helps prevent invalid triangle results.
Students can use it to verify classwork. Teachers can use it for examples. Engineers, estimators, and technical users can use it for quick side checks. Because the output includes steps and formulas, it is also useful for learning and explanation. The example data table gives sample values before you start.
The page includes CSV and PDF download options. Those features help when you need a saved record, printed worksheet, or shared result. The graph gives a simple visual comparison of the triangle sides. Together, these features make the calculator more complete than a basic one-step solver.
It supports right triangles, SAS problems, angle-side-angle problems, and perimeter-based triangle calculations. Each method is designed for a different set of known values.
Yes. The right triangle method lets you enter any two sides and leave one blank. The script calculates the missing side using the Pythagorean theorem.
The calculator checks the entered values. If the numbers create an impossible triangle, it shows a clear validation message instead of a false answer.
No. It also shows all side values, perimeter, area, steps, the active formula, and any extra angle information when the method allows it.
In every right triangle, the hypotenuse sits opposite the right angle. It is always longer than either leg, so the script validates that rule.
Yes. After a successful calculation, the page shows buttons to download the result as CSV or PDF. Both options are placed with the result section.
The page shows a Plotly bar chart for sides a, b, and c. It helps you compare the triangle lengths visually after calculation.
Yes. The page includes the formula used, short steps, an example table, and method notes. That makes it useful for both practice and review.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.