Quick start
Most popular calculators
Compound interest calculatorSavings and investment growth with contributions.Percentage calculatorPercent of, change, and difference.Loan calculatorMonthly payment and amortization.BMI calculatorBody mass index and healthy weight range.Triangle calculatorSSS, SAS, right triangle — sides, angles, area.Tip calculatorTip, total, and split the bill.ROI calculatorReturn on investment and annualized rate.Octagon calculatorRegular octagon and three diagonals.
The directory
Calculator categories
Find a calculator by what you need to calculate. Each tool is built around a specific problem, with the formula and result shown clearly on the calculator page.
Finance
Money, investing, borrowing and savings.
Math
Everyday and advanced mathematical calculations.
Percentage calculatorPercent of, change, and difference.Ratio calculatorEquivalent ratios, simplify, split.Average calculatorMean, median, mode, range.Fraction calculatorAdd, subtract, multiply, divide fractions.GCF & LCM calculatorGreatest common factor and least common multiple.Exponent & root calculatorPowers, square root, cube root, nth root.Logarithm calculatorlog base b, log10, ln, antilog.Scientific notation calculatora × 10^n and engineering notation.Rounding calculatorDecimals, sig figs, half-up and half-even.Significant figures calculatorCount and round to n sig figs.Modulo calculatora mod n remainder and quotient.Standard deviation calculatorSample s, population σ, variance, mean.Z-score calculatorz = (x − μ) / σ and tail areas.Combination & permutation calculatornCr, nPr, with and without repetition.Quadratic equation calculatorax² + bx + c = 0, discriminant, vertex.
Geometry
Shapes, measurements, areas, volumes and formulas.
Triangle calculatorSSS, SAS, right triangle — sides, angles, area.Circle calculatorRadius, circumference, area, arc, sector.Sphere calculatorRadius, surface, volume — and π form.Cylinder calculatorVolume, lateral and total surface.Cone calculatorVolume, slant, lateral and total surface.Pyramid calculatorSquare or rectangular — volume and surface.Rectangular prism calculatorBox volume, surface, space diagonal.Ellipse calculatorArea, Ramanujan circumference, eccentricity.Regular polygon calculatorn-gon area, perimeter, apothem, interior angle.Trapezoid calculatorArea, midsegment, isosceles leg.Parallelogram calculatorArea from sides and angle, or base and height.Rhombus calculatorArea from diagonals or side and angle.Rectangle calculatorArea, perimeter, diagonal.Square calculatorSide, area, diagonal, inradius, circumradius.Kite calculatorDiagonals, sides, area.Cube calculatorVolume, surface, both diagonals.Annulus calculatorRing between two circles.Sector calculatorPizza slice — area, arc, chord, segment.Segment calculatorCap between chord and arc.Frustum calculatorTruncated cone — volume and surfaces.Torus calculatorDonut volume and surface.Hexagon calculatorRegular hexagon from any one measure.Pentagon calculatorRegular pentagon and golden diagonal.Octagon calculatorRegular octagon and three diagonals.Tetrahedron calculatorRegular tetrahedron — volume a³/(6√2).Octahedron calculatorEight triangles — dual of the cube.Dodecahedron calculatorTwelve pentagons — dual of the icosahedron.Dodecagon calculator12-gon — five diagonal lengths.Icosahedron calculatorTwenty triangles — D20.Pythagorean theorem calculatora² + b² = c² from any two sides.Law of cosines calculatorc² = a²+b²−2ab cos C.Law of sines calculatora/sin A = 2R.Heron formula calculatorArea from three sides.
Everyday
Useful calculations for common situations.
Health
Simple health and fitness calculations.
Business
Practical calculations for business decisions.
About ST Calculator
Useful calculations,
without the clutter.
without the clutter.
ST Calculator is a growing collection of practical online calculators. The goal is straightforward: make calculations easy to use and easy to understand.
We keep the interface focused on the calculation itself, while giving you enough explanation to understand where the result comes from.
Clear inputs and outputsTransparent formulasWorks in your browserFree and easy to use