Zone · 39 rides

Calculators

Health, money, maths and everyday numbers - with the formula shown, not hidden.

Percentage CalculatorWhat is X% of Y, X is what % of Y, percentage change, increase or decrease by a percent, value before a change and percentage points – seven cards that work at once.
Loan CalculatorMonthly payment, total interest and a full amortization schedule for any fixed-rate loan in any currency. Add fees for the APR, or an extra payment to see what you save.
VAT CalculatorAdd VAT to a net price or take it out of a gross price at any rate. Preset chips for common rates (5–27%), the tax amount, and the same amount shown at other rates.
BMI CalculatorCalculate your BMI from height and weight (metric or imperial) with the WHO adult category, the healthy weight range for your height and BMI prime.
Ideal Weight CalculatorIdeal body weight for your height and sex by the Devine, Robinson, Miller and Hamwi formulas, plus the BMI 18.5–24.9 healthy range, in kg or lb.
Body Fat CalculatorBody fat percentage from neck, waist and hip tape measurements with the US Navy method, plus ACE category, fat and lean mass and a BMI-based estimate.
Body Surface Area CalculatorBody surface area in m² from height and weight by five formulas – Mosteller, Du Bois, Haycock, Gehan & George and Boyd – side by side, metric or imperial.
TDEE CalculatorDaily calorie needs from Mifflin–St Jeor, Harris–Benedict or Katch–McArdle BMR and activity level, with weight-loss and gain targets and macro grams.
Fat-Burning Heart Rate CalculatorFat-burning zone (60–70% of max heart rate) and five training zones by age with the Tanaka, Fox or Gellish formula, plus Karvonen when you know your resting rate.
Waist-to-Hip Ratio CalculatorWaist divided by hip compared with the WHO cut-offs (0.90 men, 0.85 women), plus waist circumference levels and the waist-to-height "half your height" rule.
Water Intake CalculatorA rule-of-thumb daily water estimate from body weight, exercise and climate in ml, litres, cups and fluid ounces, next to the EFSA and US adequate intake values.
Sleep CalculatorBest bedtimes for a wake-up time, wake-up times for a bedtime, or what to aim for if you sleep now – in 90-minute cycles plus 15 minutes to fall asleep.
Pace CalculatorRunning pace per km or mile from time and distance, finish time from a pace, or distance covered – with 5K, 10K, half and marathon presets, speed and even splits.
BAC CalculatorEstimate blood alcohol content from your drinks, weight, sex and hours since the first drink with the Widmark formula, plus the time back to 0.00 and under common limits.
Blood Pressure CalculatorBlood pressure category under the 2017 ACC/AHA and 2024 ESC guidelines, with pulse pressure, mean arterial pressure, what to do next and a reading log on your device.
Blood Type CalculatorWhich ABO and Rh blood types a child can inherit from two parents, with probabilities and Punnett squares – or check whether parents could have a child of a given type.
Ovulation CalculatorEstimate your ovulation day and six-day fertile window from your last period, cycle length and luteal phase, plus the next three periods on a cycle calendar.
Pregnancy CalculatorDue date from your last period (Naegele’s rule, cycle-adjusted), conception date or IVF transfer, plus weeks pregnant, trimester, milestone dates and a countdown.
Pet Age CalculatorDog or cat age in human years with the size-based veterinary chart, the 2020 epigenetic formula (16 ln(age) + 31) for dogs and the 15/9/4 cat chart – plus the life stage.
Wind Chill CalculatorFeels-like temperature from air temperature and wind with the NWS / Environment Canada wind chill formula and frostbite bands, plus a heat index mode for hot, humid days.
Compound Interest CalculatorSee how savings grow with daily, monthly, quarterly, yearly or continuous compounding, optional regular deposits, and a year-by-year table of interest earned.
Savings Goal CalculatorFind the monthly deposit needed to reach a savings target by a deadline, or how long a fixed monthly deposit takes, with interest and a progress bar.
Tip CalculatorWork out the tip and total for any bill, split it between people, round up to whole amounts and tip on the pre-tax amount if you prefer.
Fuel Cost CalculatorCalculate the fuel and cost of a trip from distance, consumption (L/100 km, km/L or mpg) and fuel price, with round trip and cost per passenger.
Electricity Cost CalculatorWhat any appliance costs to run from its watts (or kW, or amps × volts), hours of use and your price per kWh – per day, month and year, for several devices at once.
Download Time CalculatorEstimate how long a download or upload takes from the file size and your connection speed, with bits vs bytes handled correctly, overhead and a table of common speeds.
Tile CalculatorWork out how many tiles and boxes you need from the room size, tile size, grout gap and waste allowance, in metric or imperial, with the cost if you know the price.
Bicycle Frame Size CalculatorFind your bike frame size from your inseam for road, mountain, hybrid and city bikes, in cm and inches, with a height-based size chart as a cross-check.
Alcohol Dilution CalculatorHow much water to add to dilute a spirit from one ABV to another, or how much spirit and water make a target volume, with the Pearson square and a contraction note.
Scientific CalculatorOnline scientific calculator with keyboard input: parentheses, powers, roots, trig in degrees or radians, logs, factorials, memory and history. Basic mode included.
Fraction CalculatorAdd, subtract, multiply and divide fractions and mixed numbers with the working shown step by step, simplified results, decimal and percent equivalents and a comparison.
Decimal to Fraction CalculatorConvert any decimal to its simplest fraction, including repeating decimals like 0.(3) or 0.1666…, with the working shown and the closest fractions for inch rulers (2–64).
GCD and LCM CalculatorFind the greatest common divisor (GCF/HCF) and least common multiple of 2 to 10 numbers, with Euclid’s algorithm written out and the prime factorisation of each number.
Circle CalculatorEnter any one of radius, diameter, circumference or area and get the other three, plus arc length, chord and sector area for a central angle, in any unit.
Cylinder Volume and Surface Area CalculatorVolume and surface area of a cylinder from its radius or diameter and height, with lateral, base and total area, and the volume in litres and US or UK gallons.
PSN Trophy Level CalculatorEnter your platinum, gold, silver and bronze trophies to get your PlayStation trophy level, total points, progress and how many trophies the next level needs.
Profit Margin & Markup CalculatorCost and price in, profit, margin and markup out – or set a target margin or markup and get the selling price, with fixed costs and a percentage fee included.
Grade & Final Grade CalculatorAdd your assessments with scores and weights to get your weighted grade, then see exactly what you need on the final exam to reach the course grade you want.
HYROX Race PlannerPlan a HYROX race: run pace, eight station times and Roxzone transitions add up to a finish time with splits – or work back from a goal time to the pace you need.