Pythagorean Theorem Calculator
Find a side. Check the right angle.
Pythagorean inputs
Find one side or check three given lengths.
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 two known legs must meet at a right angle. A rectangle's width and height can be used here to find its diagonal.
Applies to every active side. Convert mixed measurements to one unit first. Changing this selector reinterprets the retained numbers.
Converts sides and perimeter. Squared-side rows use the square of this unit.
Area converts independently, including international acres and hectares.
Exact expressions and classification stay unchanged. Very small nonzero values retain scientific views.
Finite decimals and fractions retain exact values. Source limits and thin-diagram omissions are explained beside the results. Checking three sides does not model measurement uncertainty.
Interpreted active measurements
Hypotenuse
Rounded side view
Area
Perimeter
Exact means exact for the entered numbers, not a claim about measurement uncertainty. No tolerance silently turns a nearly right triangle into a right triangle.
Sources allow sixty significant decimal digits or sixty digits per fraction integer, up to one hundred eighty characters and scientific exponents from negative one hundred through positive one hundred. Exact intermediate numerators and denominators are limited to eighteen hundred digits.
Small nonzero results retain a scientific view instead of being displayed as zero. Radical extraction checks small square factors and a remaining perfect square; it does not promise arbitrary integer factorization.
Verified right triangle diagram
Calculation step by step
Identify the active measurements
The hypotenuse is opposite the right angle. The two given lengths use the shared source unit; they are not independent answers to unrelated problems.
Add the two leg squares
All decimal and fraction sources are exact rational numbers. Squaring and subtraction occur before any decimal rounding, even when two given sides are almost equal.
Take the positive length
Lengths use the nonnegative square-root branch. A negative algebraic root is not a second physical side length. Radical extraction is verified but bounded; a large remaining radicand need not be fully factored.
Calculate coverage and the boundary
The area uses the perpendicular legs from this same triangle. Perimeter adds all three exact side lengths.
Convert dimensions before rounding
A length factor and an area factor have different dimensions. Each output is rounded independently from its exact expression. Precision changes the decimal view, not the source or the classification.
All side and area results
Squared quantities use the square of the output length unit. Area has its own output unit. Rounded views never replace exact values.
| Quantity | Exact value | Rounded view | Interpretation |
|---|---|---|---|
| Leg | Converted known source length. | ||
| Leg | Converted known source length. | ||
| Hypotenuse | Solved positive root. | ||
| Area | Half the product of the perpendicular legs. | ||
| Perimeter | Exact sum evaluated before rounding; no rounded side is reused. | ||
| Squared side | Squared output length units, independent of the area-output selector. | ||
| Squared side | Squared output length units, independent of the area-output selector. | ||
| Squared side | Squared output length units, independent of the area-output selector. | ||
| Sum | Exact sum of the two shorter-side squares in check mode. | ||
| Residual | Zero means right; positive means acute; negative means obtuse after the strict triangle check. |
Side in all length units
| Unit | Exact 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 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
- Find hypotenuse
- 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
Make a right-triangle relationship useful
Recover the one side you are missing
Start from the two measurements you actually know. Perpendicular legs determine their hypotenuse, while a hypotenuse and a shorter leg determine the remaining leg. The selected method exposes only required fields and retains its own editor values. Exact squares, a positive root and a coherent result table replace the confusion of two unrelated sample triangles presented as one calculation.
Test a set of three supplied lengths
Use the converse as a separate check rather than forcing every input into a right-triangle model. The checker accepts any order, sorts lengths explicitly and validates that they form a positive-area triangle. Comparing exact squares distinguishes right, acute and obtuse cases. Non-right results keep their own valid area calculation and never acquire an invented perpendicular-leg diagram.
Interpret diagonals, coverage and boundaries
A flat rectangle diagonal is the hypotenuse formed by its perpendicular width and height. The calculator reports the associated triangle's coverage and boundary length with independent dimensional outputs. Remember that this triangular area is half the rectangle's area. Conversion tables translate a coherent idealized model into useful units while source strings, assumptions and exact expressions remain inspectable.
The theorem and its converse, step by step
Add the two leg squares
For perpendicular legs and , the squares sum to . The positive root is the hypotenuse . Coverage and perimeter describe this same triangle, rather than a separate example with unrelated measurements.
Subtract when the hypotenuse is known
With hypotenuse and known leg in a common unit, the missing leg is . A square root of a difference is not the difference of the square roots. An equal hypotenuse and leg would yield a collapsed figure, which the positive-side solver rejects.
Preserve the radical in the boundary length
Two unit legs give hypotenuse and perimeter . A six-place hypotenuse view is approximately , but it never replaces the radical. Each output is rounded from its exact quantity. The associated triangle covers half a square of the source length unit.
Test the longest side and distinguish non-right cases
After sorting , first require . Sides have zero residual. Sides are acute, while sides are obtuse. The obtuse example has Heron area , rather than the product of its two shorter sides divided by two.
Convert each dimension with its own factor
The default hypotenuse becomes and its area becomes . Length uses a factor of , while area uses . Changing output units preserves the figure; changing the source selector reinterprets the original numeric strings.
Why exact sources and visible assumptions help
Classification comes before rounding
- Strict positivity and triangle inequalities reject collapsed or impossible checked figures.
- Exact rational squares preserve tiny differences between a leg and hypotenuse.
- A nearly zero residual remains nonzero; no hidden tolerance certifies a right angle.
- The corner marker appears only on a verified right triangle at an honest common scale.
The complete mathematical record stays available
- Fractions and verified radicals remain beside independent rounded decimal views.
- Perimeter uses an exact additive expression, never a sum of rounded displayed sides.
- Seventeen physical length definitions and nineteen area definitions convert independently.
- Sharing, plain copying, CSV and browser PDF retain the active problem and working.
Right-triangle reasoning for lessons and measured layouts
Students choosing addition or subtraction
Match the unknown side to its role before choosing an operation. Adding leg squares finds the longest side; subtracting a leg square from the hypotenuse square finds the other leg. Ordered working connects the rearranged identity to actual substitutions. Fractional and radical examples show why keeping an exact answer differs from simply choosing more decimal places.
Teachers explaining the converse
Compare a solved perpendicular-leg problem with a three-side test. The first assumes a right angle; the second establishes whether typed lengths imply one. Acute, right and obtuse examples demonstrate the squared-length residual's sign. The vector illustration shares one physical scale in both directions, and printed working keeps the source interpretation beside the equations.
People estimating flat diagonals and clearance
Use compatible measurements that genuinely meet at a right angle, such as a rectangle's width and height or a vertical rise and horizontal run. A sloping edge is not automatically a perpendicular leg. The result is an ideal plane-geometry estimate; measurement uncertainty, safety factors, material allowances and installation constraints need additional evidence beyond the typed dimensions.
How it works in three quick steps.
Choose the missing side or check three lengths
Choose hypotenuse for two known perpendicular legs, or the matching missing-leg mode for a known hypotenuse and leg. Check mode accepts three lengths in any order. Enter decimals or integer fractions and select a common source length unit. Read the interpreted measurements before using the answer.
Inspect the exact squared-length working
Adding leg squares finds a hypotenuse; subtracting a leg square from the hypotenuse square finds the other leg. Check mode sorts lengths, validates the strict triangle inequality and compares squares exactly. Follow the positive root and the classification before interpreting area or a diagram.
Convert and preserve the full result
Choose length and area outputs independently. Compare exact expressions with rounded views, inspect the equal-scale diagram where available, and retain the original source strings. Copy working, share the active problem, download every conversion as CSV or use browser printing to save a mathematical PDF.
Keep the original problem with the answer
Download complete exact working
CSV includes active input strings, the method, units and exact classification. Result rows retain exact expressions and separately rounded views. Rational certificates identify direct values, while additive certificates describe a perimeter containing a radical. Hidden conversions remain included. Formula-safe cells prevent source text from becoming a spreadsheet instruction when the record is opened for comparison.
Print a solution or save PDF
Browser printing removes editor controls and supporting promotional sections. The available equal-scale diagram, equations, result details and visible conversion tables remain printable. Use the browser's Save as PDF destination and inspect paper size before sharing. Exceptionally long expressions use an explicit notice directing readers to complete CSV values instead of clipping a large number.
Share one reproducible active problem
A shared fragment records the chosen method, required source strings and current unit and display choices. Other editor buffers are excluded, so a recipient loads one defined problem. Strict importing rejects hidden measurements, extra fields and duplicate fragment keys. Reset restores familiar defaults and clears the fragment. Plain copying preserves readable mathematics for destinations without formula typesetting.
Frequently Asked Questions
What is the Pythagorean theorem formula?
How do I find a missing leg?
Can I check whether three sides form a right triangle?
Why does an almost right triangle fail the exact check?
Can I enter fractions and scientific notation?
Are radicals and rounded values both exact?
Can I use this tool for a rectangle diagonal?
Why do area and squared-side rows use different units?
Why is there sometimes no triangle diagram?
What is included when I download, print or share?
About this exact Pythagorean theorem calculator
Toolarithm's Pythagorean Theorem Calculator separates two mathematical questions that often look similar on a worksheet. Finding a missing side begins with the assumption that the legs meet perpendicularly. Checking three lengths instead asks whether a valid triangle with those lengths would have a right angle. Keeping these workflows distinct makes the source interpretation as important as the final number. The tool validates the required measurements, identifies the operation and retains a traceable exact expression for each result.
Finite decimal and integer-fraction sources are interpreted as rational numbers. Their squares and differences are calculated before decimal rounding, especially useful when a known leg lies close to the hypotenuse. The positive square root represents the missing physical length. Radical expressions are verified against exact squared quantities, while rounded views are calculated independently. A perimeter containing an irrational side is evaluated as an exact rational-plus-radical expression, so a displayed approximation never becomes a hidden input to a later quantity.
The checker sorts lengths explicitly, rejects collapsed or impossible outlines, and classifies valid triangles from the exact squared-length residual. Non-right triangles use Heron area rather than an unjustified perpendicular-leg product. The equal-scale diagram is reserved for right triangles with visible leg proportions; a notice explains omitted outlines. Independent length and area outputs, preserved source records and complete CSV working support study and reproducible comparisons. The calculator models ideal plane geometry and exact typed numbers; it does not infer measurement uncertainty or certify a physical construction tolerance.
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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