Right Triangle Calculator
Connect the sides to the angles.
Right triangle inputs
Choose two known measurements to solve one right triangle.
Each method retains its own values. Only active fields are validated.
Use a finite decimal, scientific e notation or an integer fraction.
Use a finite decimal, scientific e notation or an integer fraction.
Units and display choices
The right angle is at the third vertex. Each side is opposite its matching uppercase angle. At least one length is needed to determine scale.
Converts angle views without reinterpreting the source problem.
Applies to every active side. Convert mixed measurements to one unit first. Changing this selector reinterprets the retained numbers.
Converts sides, perimeter, altitude, projections and circumradius.
Area converts independently, including international acres and hectares.
Exact side-based expressions stay unchanged. Numerical trigonometry uses at most ten places; nonzero small values retain scientific views.
Side pairs retain exact squared magnitudes. Special degree and pi-radian angles retain exact geometry. General trigonometry is approximate, with explicit boundary limits. The source and output angle selectors are independent.
Interpreted active measurements
Solved right triangle
Rounded hypotenuse view
Area
Perimeter
Acute angle
Complementary acute angle
Sides, coverage and acute-angle ratios retain exact rational or verified radical expressions. Angle views are numerical unless a recognized exact angular relationship is available.
Exact means exact for the typed numbers, without measurement uncertainty. Sources support sixty significant decimal digits or sixty digits per fraction integer, one hundred eighty characters and exponents from negative one hundred through positive one hundred. Exact intermediate magnitudes are limited to eighteen hundred digits.
Root extraction is verified but bounded, not a promise of complete integer factorization. Small nonzero values retain scientific views. Exact displays support twelve decimal places; numerical trigonometry uses at most ten.
Opposite sides and acute angles
Calculation step by step
Identify opposite and adjacent sides
The third angle is right. Each lowercase side is opposite its matching uppercase angle. A hypotenuse never serves as the adjacent leg in a tangent ratio.
Find the hypotenuse from perpendicular legs
Exact squared source lengths are added before the positive root is evaluated. The source unit applies to both legs.
Evaluate both acute-angle ratios
Cosecant, secant and cotangent are the reciprocals of sine, cosine and tangent. Positive nondegenerate legs keep all six acute-angle ratios finite.
Recover coverage and derived distances
Coverage uses perpendicular legs. The altitude and projections refer to the hypotenuse line, not to an unrelated base-height example. Projections sum to the hypotenuse.
Convert dimensions independently
Output selectors convert numeric measurements of the same triangle. Changing a source-unit or input-angle convention instead reinterprets the retained input numbers. Length factors are squared before conversion to an independent area unit.
All triangle measurements
The first value retains an exact expression where available. Numerical trigonometry is marked as approximate. The rounded column never becomes a new source.
| Quantity | Exact or numerical value | Rounded view | Interpretation |
|---|---|---|---|
| Leg | Exact positive length from the selected geometry. | ||
| Leg | Exact positive length from the selected geometry. | ||
| Hypotenuse | Exact positive length from the selected geometry. | ||
| Area | Half the product of the perpendicular legs of this same triangle. | ||
| Perimeter | Sum of the full side expressions; displayed rounded sides are not reused. | ||
| Semiperimeter | Half the perimeter, evaluated before rounding. | ||
| Altitude to hypotenuse | Perpendicular distance from the right vertex to the hypotenuse line. | ||
| Circumradius | Half the hypotenuse; its midpoint is the circumcenter. | ||
| Projection | Projection of the first leg onto the hypotenuse. | ||
| Projection | Projection of the second leg onto the hypotenuse. | ||
| Acute angle | Numerical inverse tangent using both perpendicular legs. | ||
| Acute angle | Numerical complement of the first acute angle. | ||
| Right angle | The defining right angle; the two acute angles are complementary. |
Six trig ratios for each acute angle
The first value retains an exact expression where available. Numerical trigonometry is marked as approximate. The rounded column never becomes a new source.
| Quantity | Exact or numerical value | Rounded view | Interpretation |
|---|---|---|---|
| Sine of first angle | Dimensionless ratio; changing length units does not change its value. | ||
| Cosine of first angle | Dimensionless ratio; changing length units does not change its value. | ||
| Tangent of first angle | Dimensionless ratio; changing length units does not change its value. | ||
| Cosecant of first angle | Dimensionless ratio; changing length units does not change its value. | ||
| Secant of first angle | Dimensionless ratio; changing length units does not change its value. | ||
| Cotangent of first angle | Dimensionless ratio; changing length units does not change its value. | ||
| Sine of second angle | Dimensionless ratio; changing length units does not change its value. | ||
| Cosine of second angle | Dimensionless ratio; changing length units does not change its value. | ||
| Tangent of second angle | Dimensionless ratio; changing length units does not change its value. | ||
| Cosecant of second angle | Dimensionless ratio; changing length units does not change its value. | ||
| Secant of second angle | Dimensionless ratio; changing length units does not change its value. | ||
| Cotangent of second angle | Dimensionless ratio; changing length units does not change its value. |
Hypotenuse in all length units
| Unit | Exact or numerical value | Rounded view |
|---|---|---|
| Nanometers | ||
| Micrometers | ||
| Millimeters | ||
| Centimeters | ||
| Decimeters | ||
| Meters | ||
| Decameters | ||
| Hectometers | ||
| Kilometers | ||
| Mils (one thousandth inch) | ||
| Inches | ||
| International feet | ||
| International yards | ||
| International miles | ||
| International nautical miles | ||
| Typographic points (one seventy-second inch) | ||
| Typographic picas (one sixth inch) |
Area in all area units
| Unit | Exact or numerical value | Rounded view |
|---|---|---|
| Square nanometers | ||
| Square micrometers | ||
| Square millimeters | ||
| Square centimeters | ||
| Square decimeters | ||
| Square meters | ||
| Square decameters | ||
| Square hectometers | ||
| Square kilometers | ||
| Square mils (one thousandth inch) | ||
| Square inches | ||
| Square international feet | ||
| Square international yards | ||
| Square international miles | ||
| Square international nautical miles | ||
| Square typographic points (one seventy-second inch) | ||
| Square typographic picas (one sixth inch) | ||
| International acres | ||
| Hectares |
Inputs saved with this calculation
- Method
- Two perpendicular legs
- Known side in angle mode
- c
- Known angle label
- A
- Input angle convention
- degrees
- Output angle convention
- degrees
- Active source strings
- Side a: 3; Side b: 4
- Source unit
- Centimeters
- Output length unit
- Centimeters
- Output area unit
- Square centimeters
- Rounded decimal places
- 6
Recover a complete right triangle from what you know
Solve perpendicular-side or hypotenuse cases
Choose the method that matches the known lengths instead of entering an unknown into an unrelated field. A pair of perpendicular legs determines the hypotenuse. A hypotenuse with either named leg determines the remaining leg through a difference of squares. Exact source arithmetic preserves small positive differences and makes the derived coverage, perimeter and projections belong to the same solved triangle.
Turn one acute angle into a side relationship
A side and a named acute angle establish both scale and shape. Identify whether the known side is opposite, adjacent or the hypotenuse relative to that angle. The solver handles both acute labels without relabelling the geometry. Independent input and output angle selectors prevent a unit conversion from silently changing the problem, while special-angle cases retain their useful exact radical forms.
Compare all six ratios at both vertices
Read sine, cosine and tangent beside their reciprocal functions, then compare the second acute vertex. The opposite and adjacent legs exchange roles when the reference angle changes. Neither a rotated drawing nor a physical unit conversion changes those dimensionless relationships. Keeping both complete ratio sets in one record helps distinguish complementary-angle identities from arithmetic coincidences in a single example.
Right-triangle formulas with connected examples
Solve a labelled side pair
With perpendicular legs and , the hypotenuse is . The same triangle has coverage and boundary length . The inverse tangent uses the ratio of the first leg to the second for angle ; reversing those roles gives the complementary angle rather than the same vertex.
Keep the reference vertex attached to each ratio
At the first acute vertex, the opposite leg is and the adjacent leg is . At the second vertex, they exchange roles. Their reciprocal functions describe the same triangle and remain finite because both perpendicular legs are positive. Converting every side to another common unit leaves the ratios below unchanged.
Recover scale from one side and an acute angle
For and , sine recovers the opposite leg and cosine recovers the adjacent leg. The hypotenuse remains the supplied measurement. Selecting angle for the same thirty-degree source exchanges the two perpendicular leg lengths. This is why a numerical angle without its vertex label does not define the same labelled problem.
Check derived distances on the hypotenuse
The default triangle's hypotenuse altitude is . The leg projections are and , which sum to the original hypotenuse. Their product equals the altitude square. These distances are constructed from the same triangle, not from an unrelated pair of base-height measurements.
Why side labels and approximation boundaries matter
The right-angle model stays explicit
- The right vertex and opposite-side convention remain visible in the source and drawing.
- Positive-leg and strict hypotenuse checks reject collapsed or impossible inputs.
- Known-side and known-angle selectors preserve their distinct geometric meanings.
- Vertex-centered arcs and equal axis scales describe the solved triangle rather than an illustrative guess.
Exact and numerical answers stay distinguishable
- Side pairs and recognized special angles retain verified rational and radical expressions.
- General trigonometric outputs are explicitly approximate, with argument reduction near angular boundaries.
- Perimeter is rounded from the full sum, without feeding rounded side views into another calculation.
- Independent angle, length and coverage outputs retain coherent dimensions and complete downloadable working.
A bridge between plane geometry and trigonometry
Students identifying opposite and adjacent
Use the vertex labels before memorizing a ratio. The adjacent side in a tangent ratio is a perpendicular leg, never the hypotenuse. Comparing both acute angles makes the complementary relationships visible. Exact fractions, equal-leg triangles and numerical angle examples show how an answer can be algebraically exact in one case and a controlled approximation in another without changing the underlying geometric definitions.
Teachers preparing connected explanations
Demonstrate why a right triangle needs scale as well as shape, and why two angles alone cannot determine actual side lengths. Follow a side-pair example into its acute angles, then reconstruct the geometry from a side-angle source. Both ratio tables, ordered equations, labelled vector geometry and preserved source conventions support a coherent explanation instead of isolated calculator outputs without a shared model.
People estimating idealized slopes and rises
A horizontal run, vertical rise and straight sloping span can form a useful plane right-triangle model when the two legs are perpendicular. Identify which measured quantity is the hypotenuse before rearranging a ratio. Real layouts may need allowances, uncertainty estimates, material constraints or safety rules beyond this idealized geometry. The calculator supplies mathematical relationships for the entered dimensions rather than certifying a physical installation.
How it works in three quick steps.
Choose two independent known measurements
Select two perpendicular legs, a hypotenuse with either named leg, or one side with an acute angle. In the angle workflow identify the known side and the named acute vertex before entering numbers. Choose the source angle convention explicitly and use a shared length unit for all supplied lengths.
Read the solved geometry and opposite-side ratios
Inspect the interpreted source and the right-angle assumption. The solver reports positive side lengths, coverage, boundary distances and complementary acute angles. Compare both acute-angle ratio tables. Exact side-based and recognized special-angle expressions remain separate from numerical trigonometry. The diagram keeps opposite-side labels and angle arcs attached to the actual solved vertices.
Convert the same triangle and save the working
Choose output length, coverage and angle conventions independently. Output changes convert a result, while source selectors reinterpret retained numbers. Inspect exact expressions and their separately rounded views. Save all quantities and hidden conversions as CSV, copy readable working, share the active problem or use browser printing to retain a mathematical PDF.
Preserve the angle convention with every result
Download every quantity and ratio
The CSV record includes dimensions, all six ratios for each acute vertex and full hypotenuse and coverage conversions. Exact squared magnitudes or root-sum certificates accompany side-based values, while numerical rows identify their approximation status. Active source strings and both angle conventions remain part of the record. Hidden conversion tables are included so a later reader can reproduce the calculation without relying on a screen view.
Print the mathematical explanation
Browser printing focuses on the solved geometry and its working, removing input controls and supporting marketing sections. Visible tables retain their headings across pages, and the vector drawing keeps its equal scale and vertex labels. Use Save as PDF and inspect paper orientation before distributing a worksheet. Very long expressions use explicit notices directing readers to complete CSV values instead of overflowing a narrow printed column.
Share a clearly defined problem
A shareable fragment stores one active method, its required measurements and the relevant side, angle and unit choices. Inactive source buffers are excluded. Extra, duplicate and malformed imported fields are rejected rather than becoming hidden measurements. Reset clears the fragment and restores familiar defaults. Plain copying produces readable mathematical text for destinations without visual typesetting while keeping the source assumptions beside the result.
Frequently Asked Questions
Which measurements determine a right triangle?
How are sides and angles labelled?
What are the six trig ratios for each acute angle?
Can I solve a side from an angle and hypotenuse?
Which results retain exact expressions?
Why are input and output angle conventions separate?
Why are zero legs or equal hypotenuse and leg rejected?
What numerical boundaries apply near a right angle?
What are the hypotenuse altitude and projections?
What does the downloadable calculation preserve?
Related calculators
About this right triangle solver and ratio reference
Toolarithm's Right Triangle Calculator connects two kinds of reasoning: recovering a perpendicular-side geometry and interpreting a side ratio relative to a named acute vertex. The right-angle assumption is explicit, and the opposite-side convention stays fixed throughout the page. That consistency matters because a sine or tangent expression cannot be interpreted correctly until the relevant angle and side roles are identified. The calculator supports each pair of known sides and a side with either acute angle, while requiring a genuine positive length to establish scale.
Finite decimal and integer-fraction side sources retain exact rational squared magnitudes. Positive roots recover the missing dimensions, and direct root-sum evaluation supplies perimeter without reusing a rounded display. Thirty-, forty-five- and sixty-degree relationships supplied in degrees or pi-radians retain exact special-angle geometry. Other angle sources require numerical trigonometry, which is labelled distinctly. Known lengths and exact degree or pi-radian relationships remain separately inspectable. The independent output-angle selector converts a solved result without silently reinterpreting the original angle field.
The complete output includes both acute-angle ratio sets, coverage, boundary distances, the altitude to the hypotenuse, its two leg projections and the circumradius. A vertex-based vector figure places acute arcs at the actual solved corners and uses equal physical scale in both directions. An explicit notice explains omitted thin outlines or unresolved extreme angle views. Source records, unit conversions, copying, sharing, CSV and native PDF support repeatable learning and comparison. The model concerns ideal plane geometry and the supplied numbers; practical measurement uncertainty and construction requirements need additional evidence beyond these mathematical relationships.
Who maintains this page
Ownership and review
Written and maintained by the Toolarithm editorial team. No review date is shown without a maintained editorial record. No independent professional review is claimed.
Methodology
Equations are checked by substituting worked examples into the stated relationship and comparing the result with the interactive implementation.
Read the editorial methodologyDates and sources
Review dates change only after a substantive method or content check.
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