PK Systems PK Systems
Calculator suite

Calculators

Free, instant calculators for health, finance and everyday math. No signup. Works in your browser.

78 calculators

Health & fitness

BMI Calculator

Calculate your Body Mass Index and see where you fall on the WHO classification scale. No sign-up, no paywall.

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Body Fat Percentage Calculator

Estimate your body fat using the U.S. Navy method or a BMI-based fallback. Free, fast, no sign-up.

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Calorie Deficit Calculator

Find the daily calorie target that matches your weight loss goal, with safe-floor guardrails. Free and instant.

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Daily Water Intake Calculator

Personalized hydration goal based on body weight, activity, climate, and life stage. Free, no sign-up.

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1 Rep Max (1RM) Calculator

Estimate your one-rep max from a sub-max set, with a full %1RM training table. Free, no login.

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Ideal Weight Calculator

Side-by-side estimates from Devine, Robinson, Miller and Hamwi formulas, plus a healthy BMI range. Free.

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Heart Rate Zones Calculator

Calculate your max HR (Tanaka, classic, or Karvonen) and 5 personalized training zones in BPM. Free.

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FFMI Calculator (Fat-Free Mass Index)

Estimate your lean muscle index and see where you stand on the natural-lifter scale.

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Race Time Predictor (Riegel formula)

Use a recent race time to predict your 5K, 10K, half-marathon and marathon — based on the classic Riegel power law.

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Protein Intake Calculator

Find your daily protein target based on goal and bodyweight, with a per-meal breakdown.

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Intermittent Fasting Schedule Calculator

Pick a protocol (16:8, 18:6, OMAD…) and see exactly when to eat and when to fast based on your last meal.

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Sweat Rate Calculator (Athlete Hydration)

Weigh in before and after training to measure your real fluid loss per hour and plan a hydration strategy.

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Wilks, DOTS & IPF GL Calculator

Convert powerlifting totals into Wilks, DOTS and IPF GL coefficient scores so lifters of any weight can be compared.

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Pregnancy Weight Gain Calculator (IOM)

Track recommended pregnancy weight gain by week, based on your pre-pregnancy BMI and the official IOM 2009 ranges.

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Waist-to-Height & Waist-to-Hip Ratio Calculator

Two simple measurements that predict cardiometabolic risk better than BMI alone — get your WHtR, WHR and body shape.

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Period & Ovulation Predictor

Project the next 12 cycles, see ovulation and fertile window dates, and plan ahead — math only, no account.

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TDEE Calculator

Estimate your Total Daily Energy Expenditure — the calories you actually burn each day. Includes cut, maintain and bulk targets.

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Macro Calculator

Split your daily calories into protein, carbs and fat — instantly. Pick your goal and get exact grams to hit each day.

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Pregnancy Due Date Calculator

Find your estimated due date, current gestational age and trimester from your last menstrual period.

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Ovulation Calculator

Estimate your most fertile days based on your last period and cycle length.

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Sleep Cycle Calculator

Find the best time to go to bed — or to wake up — based on 90-minute sleep cycles, so you wake feeling refreshed instead of groggy.

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Running Pace Calculator

Pace, time, distance, and race-time predictions — switch the mode and we'll solve for whatever's missing.

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Money & finance

Loan Calculator

Estimate your monthly payment, total cost, and total interest on any fixed-rate loan.

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Compound Interest Calculator

See how your money grows when interest earns interest. Add monthly contributions to project your wealth over time.

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Mortgage Calculator

Estimate your monthly mortgage payment including principal, interest, taxes, insurance, and HOA. See how rate and term change the total cost of your home loan.

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Tip Calculator

Work out the tip, the total bill, and what each person owes — split a check fairly in seconds.

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Discount Calculator

Find the sale price, the original price, and exactly how much you save — including stacked Black Friday-style "extra X% at checkout" deals.

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Hourly to Salary Calculator

Convert an hourly wage to annual salary — or the other way around — with paid-vacation, weekly, monthly, and daily breakdowns.

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Auto Loan Calculator

Estimate your monthly car payment, total interest, and payoff date — including down payment, trade-in, and sales tax.

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Credit Card Payoff Calculator

See how long it takes to pay off a credit card — or what monthly payment you need to be debt-free by a target date.

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Net Worth Calculator

Add up your assets and liabilities to see your real net worth — privately, in your browser.

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Dollar-Cost Averaging Calculator

Project the future value of regular contributions — see how a steady investing habit compounds over time.

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Profit Margin Calculator

Calculate gross margin, markup, and the price you'd need to charge to hit a target margin.

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Brazil CLT Net Salary Calculator (2026)

Brazil-specific tool. Compute the take-home pay for a CLT employee under the 2026 income-tax reform (full exemption up to R$5,000 gross).

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Brazil CLT Severance Calculator (2026)

Brazil-specific tool. Compute exactly what's owed at the end of a CLT employment relationship.

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Brazil 13th-Salary Calculator (2026)

Brazil-specific bonus. Compute the November and December installments under the 2026 IR reform.

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Brazil INSS Calculator (2026)

Brazil-specific. Compute the social-security contribution for a CLT employee under the progressive 2026 bands.

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Brazil Overtime Calculator (2026)

Brazil-specific. Compute 50% (weekday) and 100% (Sunday/holiday) overtime, plus night-shift bonus and DSR reflex.

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Spain Net Salary Calculator (IRPF 2026)

Estimate your monthly take-home pay after Social Security and IRPF, including autonomous community adjustments.

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US Paycheck Calculator 2026

Estimate your federal, FICA and state tax withholdings to see your real take-home pay per pay period.

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Crypto Profit Calculator

Compute your gain or loss in seconds: buy price, sell price, quantity and exchange fees.

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Mortgage Refinance Break-Even Calculator

Should you refinance? See how many months it takes for the new payment to repay the closing costs.

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How Much House Can I Afford?

Get the maximum home price your income can support using the 28/36 DTI rule with property tax, insurance and HOA.

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Mortgage Amortization Schedule Calculator

See every payment of your loan: principal, interest and remaining balance for all 360 months of a 30-year mortgage.

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50/30/20 Budget Calculator

Split your monthly take-home into needs, wants and savings using Senator Warren’s rule. Adjust the percentages to fit your life.

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Inflation Calculator (US, BR, EU)

Convert any amount of money between any two years using official CPI data — see what $100 in 1980 is worth today.

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Fuel Trip Cost Calculator

Compute how much fuel a trip burns in dollars (or euros, reais), supporting MPG, km/L and L/100km.

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Everyday math

Age Calculator

Calculate your exact age in years, months, and days from any birth date — plus your total months, weeks, days, hours, and minutes alive, and the days until your next birthday.

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Percentage Calculator

Three percentage calculations in one tool: what is X% of Y, X is what percent of Y, and the percent change between two numbers. Instant results, no signup.

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Date Difference Calculator

Find the exact span between any two dates — in years, months, days, weeks, hours, and minutes.

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Rule of Three Calculator

Solve any direct or inverse proportion in seconds — fill in three values and we find the fourth.

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Pet Age Calculator

How old is your dog or cat in human years? Get the modern, size-aware estimate — not the outdated 7× rule.

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Cat Age Calculator

Convert your cat's age into human years using the modern feline aging curve — and see exactly which life stage they're in.

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Dog Age Calculator

How old is your dog in human years? The modern, size-aware formula — small dogs and giant breeds age very differently after year two.

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How Many Days Have I Been Alive?

Your life in days, hours, minutes and seconds — counting up live. Plus heartbeats, breaths, full moons seen, and the next 1,000-day milestone.

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Reading Time Calculator

How long will it take to read this? Paste any text or enter a page count — we'll show minutes, hours, and word count at slow, average or fast WPM.

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Coffee Brew Ratio Calculator

Pick a brew method, set your beans or water, and get the right ratio plus a grind and time guide.

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Caffeine Calculator — When Can I Sleep?

Add what you drank today and see how much caffeine is still in your system — and the time it drops below the sleep-safe threshold.

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Wedding Anniversary Calculator

How long you've been married, when your next anniversary lands, and the traditional gift theme for every year up to 50.

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Final Grade Calculator

What score do you need on the final exam to land your target grade — or what will your course grade be if you ace (or bomb) the final?

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Cups to Grams Converter

Convert cooking measurements between cups, grams, ounces and milliliters using accurate ingredient densities.

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Fuel Consumption Calculator

Work out your real-world MPG, km/L or L/100km, or convert between any of those units instantly.

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Time Card Calculator

Add up daily and weekly work hours, including overnight shifts and breaks. Optional pay total.

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Mulch, Soil & Gravel Calculator

Work out exactly how much mulch, soil or gravel your beds need in cubic yards, cubic meters and bags.

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Concrete Calculator

Estimate concrete volume and bag count for slabs, footings and columns in yards or cubic meters.

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BTU Air Conditioner Sizer

Find the right AC size for your room based on area, ceiling, sun exposure and climate.

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Fraction Calculator

Add, subtract, multiply or divide two fractions and get the simplified result with worked steps.

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Standard Deviation Calculator

Paste numbers and instantly get mean, median, mode, range, sample SD, population SD and variance.

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Days Until Calculator

A live countdown to any future date — Christmas, New Year, your wedding, a holiday, anything.

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Recipe Scaler

Scale any recipe up or down in seconds. Type or paste ingredients and pick a new serving size.

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Oven Temperature Converter

Switch between Fahrenheit, Celsius, fan-assisted Celsius, and British Gas Mark in one tap.

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Days Sober Counter

Track your time, your milestones, and the savings — one day at a time.

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Cost of Smoking Calculator

See what cigarettes cost over a lifetime — and what the same money becomes if you invest it instead.

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Shoe Size Converter

Convert between US, UK, EU, Japanese, and centimetre sizes for men's and women's shoes.

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Chinese Zodiac Sign Calculator

Find your animal, element, and yin/yang from your birth date — using the lunar calendar, not January 1.

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Roast Cooking Time Calculator

Cooking-time and resting-time estimates for turkey, chicken, pork, brisket, ham, and prime rib.

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Jet Lag Recovery Calculator

Estimate recovery days and get a 3-day light, sleep, and meal plan based on your direction of travel.

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Half-Your-Age-Plus-Seven Calculator

The classic social rule for an acceptable dating age range — calculated, with a wink.

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