Free, fast calculators and checkers built by HawkInc, from math, science and accounting solvers to lab, water, Etsy and everyday tools. Many were designed with an accredited testing-lab background. They run in your browser, with no sign-up, and nothing you enter is stored.
Math & Algebra Calculators
Scientific CalculatorTrig, logs, powers, roots and factorials, with degree/radian modes and history.
Trigonometry CalculatorExact sin, cos and tan values, plus right and oblique triangle solvers.
Quadratic Equation SolverExact roots, discriminant, vertex and graph, with step-by-step working.
System of Equations SolverSolve 2, 3 or 4 simultaneous equations with Cramer’s rule.
Matrix CalculatorDeterminant, inverse, multiplication, rank and RREF in exact fractions.
Circle CalculatorArea, circumference, arcs and the equation of a circle.
Ellipse CalculatorFoci, vertices, eccentricity, area and perimeter, with a graph.
Parabola CalculatorVertex, focus, directrix and latus rectum for any parabola.
Probability CalculatorTwo events, binomial, normal distribution, z-scores, nPr and nCr.
Set CalculatorUnion, intersection, complement and power set with Venn diagrams.
Chemistry Calculators
Molar Mass Calculatorg/mol, percent composition and grams-to-moles for any formula.
Chemical Equation BalancerBalance molecular, ionic and redox equations with an atom check.
Molarity, Dilution & pH CalculatorMake solutions, solve C₁V₁ = C₂V₂ and convert pH, pOH and [H⁺].
Ideal Gas Law CalculatorPV = nRT and the combined gas law with unit conversion.
Density CalculatorFind density, mass or volume in any unit.
Specific Heat Calculatorq = mcΔT for heat, mass, specific heat or temperature change.
Half-Life CalculatorRadioactive decay, remaining amount, decay constant and a curve.
Buffer pH CalculatorHenderson–Hasselbalch pH and buffer recipes.
Titration CalculatorUnknown concentration from titre volume and mole ratio.
PPM Converterppm, ppb, mg/L, % and molarity conversions.
Empirical Formula CalculatorEmpirical and molecular formula from percent or grams.
Limiting Reactant CalculatorLimiting reagent, theoretical yield, excess and percent yield.
Beer-Lambert Law CalculatorA = εlc for concentration from absorbance, plus %T.
Physics Calculators
Kinematics (SUVAT) CalculatorSolve equations of motion and projectile range, height and time.
Ohm’s Law CalculatorVolts, amps, ohms and watts, resistor networks and kWh cost.
Force CalculatorNewton’s second law F = ma and weight.
Energy, Work & Power CalculatorKinetic and potential energy, work and power.
Momentum & Impulse Calculatorp = mv, impulse and collisions.
Pressure CalculatorP = F/A and fluid pressure ρgh.
Wave CalculatorWave speed, frequency, wavelength and period.
Lens & Mirror CalculatorThin lens equation, image distance and magnification.
Centripetal Force CalculatorCircular motion force, speed, radius and acceleration.
Gravitational Force CalculatorNewton’s law of gravitation between two masses.
Snell’s Law CalculatorRefraction angles, refractive index and critical angle.
Hooke’s Law CalculatorSpring force, extension, spring constant and stored energy.
Coulomb’s Law CalculatorElectric force between charges, field and potential energy.
Temperature ConverterCelsius, Fahrenheit, Kelvin and Rankine.
Biology Calculators
Punnett Square CalculatorMonohybrid to trihybrid crosses with genotype and phenotype ratios.
DNA Sequence CalculatorComplement, mRNA, protein translation, GC content and Tm.
Hardy-Weinberg Calculatorp, q, p², 2pq, q², carriers and an equilibrium test.
Chi-Square CalculatorGoodness of fit for 3:1 and 9:3:3:1, and independence tests.
Bacterial Growth CalculatorGeneration time, doubling and growth curves.
Population Growth CalculatorExponential and logistic growth with carrying capacity.
Serial Dilution CalculatorTube-by-tube dilutions and CFU/mL from plate counts.
Hemocytometer CalculatorCells per mL, seeding volume and trypan blue viability.
Microscope Magnification CalculatorActual size, image size, total magnification and field of view.
Accounting & Business
Loan EMI CalculatorMonthly installment, total interest and an amortization schedule.
Break-Even CalculatorBreak-even units and sales, contribution margin and margin of safety.
Depreciation CalculatorStraight-line, WDV, double declining, SYD and units-of-production schedules.
Fun & Curious Calculators
My Life in NumbersHeartbeats, days lived and more, all worked out from your birthday.
How Long Would It Take?Walk across America, cycle around the world or count to a million.
How Many Fit?Jelly beans in a jar, ping pong balls in a room, balloons in a car.
Birthday Fun FinderGolden and half birthdays, birth flower, birthstone and zodiac signs.
Odds Comparison CalculatorIs it more likely than being struck by lightning or winning the lottery?
Weight in Gold CalculatorFind out what you are worth in gold or silver, in any currency.
Treasure Map MakerMake a one-of-a-kind printable treasure map for a kids’ treasure hunt.
Secret Code MakerEncode and decode secret messages with Caesar, Pigpen, Morse and more.
Secret Santa Budget CalculatorA fair spending limit for your group, plus a free online name draw.
Quran Khatam PlannerHow many pages a day to finish the Quran by your chosen date.
Laboratory & Quality Control
HorRat Calculator (Horwitz Ratio)Horwitz predicted RSD and HorRat value from your concentration and observed precision.
Spike Recovery CalculatorPercent recovery for matrix spikes, with dilution correction and AOAC acceptance ranges.
Proficiency Testing Score Calculator (z, z′, ζ, En)z, z′, zeta and En scores from ISO 13528 with pass/warning/fail verdicts.
LOD & LOQ CalculatorLOD/LOQ from a calibration curve (ICH 3.3σ/S) or blank replicates, including EPA MDL.
Westgard Rules Checker & Levey-Jennings ChartPlot a Levey-Jennings chart and flag 1-2s, 1-3s, 2-2s, R-4s, 4-1s and 10x violations.
Measurement Uncertainty Calculator (GUM Budget)Free GUM uncertainty budget: Type A/B components, Welch–Satterthwaite and expanded U.
Water, Soil & Home Testing
SAR Calculator (Sodium Adsorption Ratio)Sodium adsorption ratio from Na, Ca, Mg with sodium, salinity and infiltration hazard ratings.
NPK Fertilizer Blend CalculatorUrea, DAP and potash needed for a target N-P-K rate, or the grade of your own blend.
Well Water Test Results InterpreterCompare your well water lab report with EPA limits and get plain-English treatment advice.
PFAS Water Test Results & Hazard Index CalculatorCheck PFOA, PFOS, GenX and other PFAS results against EPA limits and calculate the Hazard Index.
Lawn Soil Test Interpreter (Lime & Fertilizer Calculator)Lime or sulfur, phosphate, potash and nitrogen plan for your lawn from a soil test report.
Water Softener Size CalculatorGrain capacity, recommended softener size and salt use from hardness and household size.
Craft & Maker Calculators
Bookbinding & Junk Journal Signature CalculatorSignatures, sheets, blank pages and printing order for handmade books and junk journals.
Leather Calculator – How Much Leather Do I Need?Square feet of leather for your pattern with waste, the right hide size and fabric-yard conversion.
Macrame Cord Length CalculatorCut length per cord, total cord and spools for wall hangings, plant hangers and more.
Embroidery Stitch Count EstimatorStitch count, machine time and price from design size, coverage and lettering.
Crochet Yarn Calculator – How Much Yarn Do I Need?Yards and skeins for blankets and projects by size, yarn weight and stitch, or from a swatch.
Candle Wax & Fragrance Oil CalculatorWax and fragrance oil per candle and per batch by vessel size, wax type and fragrance load.
Cross Stitch Fabric Size CalculatorFinished design size and fabric to cut for any stitch count on Aida, evenweave or linen.
Etsy, KDP & Printable Seller Tools
KDP Cover Size & Spine Width CalculatorPaperback spine width, full cover size with bleed and pixels at 300 DPI.
Etsy Title & Tag CheckerChecks 13 tags, 20-character limits, duplicates, invalid characters and title length.
Etsy Fee & Profit CalculatorEvery Etsy fee, profit and margin per sale, plus the price you need for a target profit.
Etsy Fees, VAT & US Tariff CalculatorEtsy commission, UK VAT and the US tariff you prepay on orders to US and UK buyers.
Print Size & DPI Calculator for PrintablesPixels for any print size at 300 DPI, the largest print size for an image, and Etsy ratio sets.
Pakistan Home & Energy
Solar System Calculator Pakistan (Size, Cost & Payback)kW size, panels, cost, savings and payback from your bill units, with 2026 net billing rates.
UPS & Inverter Battery Backup CalculatorBackup hours from your battery and load, or the battery size needed for a target time.
Shaadi Budget Calculator (Pakistani Wedding)Mehndi, Baraat, Walima and Nikah costs by guests and per-head, plus dresses, jewellery and more.
Water Tank Capacity Calculator (Litres & Gallons)Litres and gallons for rectangular, round and horizontal tanks, partial fill and days of supply.
Islamic Calculators
Aqiqah Calculator – Date, Animals & Cost7th/14th/21st day dates with Hijri date, animals needed, total cost and hair sadaqah.
Qaza Namaz Calculator – Missed PrayersCount missed prayers (Qaza Umri) including Witr, and plan how long making them up will take.
Islamic Inheritance Calculator (Mirath / Faraid)Quranic shares for spouse, children, parents and siblings after debts and wasiyyah, with 'awl and radd.
Health & Fitness
BMI CalculatorBody mass index with WHO and Asian cut-offs and your healthy weight range.
Calorie Calculator (BMR & TDEE)Daily calories to lose, keep or gain weight.
Protein Intake CalculatorGrams of protein per day for your weight and goal, per meal.
Macro CalculatorProtein, carbs and fat grams for balanced, low-carb or keto diets.
Food Nutrition CalculatorCalories, protein, carbs, fat and fibre in your meal, incl. roti and daal.
Water Intake CalculatorDaily water target for your weight, exercise and climate.
Body Fat CalculatorUS Navy tape method body fat %, fat mass and lean mass.
Ideal Weight CalculatorIdeal body weight for your height from 4 formulas.
Heart Rate Zone CalculatorMax heart rate and 5 training zones with the Karvonen method.
Calories Burned CalculatorCalories burned walking, running, cricket and 22 more activities.