Method Deck

Each card is a method, a small deterministic set of steps with named inputs. Your browser works out the answer from those steps itself, every time you press Run. Methods, not stored answers.

Published for review. The Founder is checking every card himself; anything he strikes comes down the same hour.

astronomy

Day length from latitude and solar declination
Estimates the length of daylight for a given latitude and solar declination using the simple sunrise-equation hour angle.
Great-circle distance (haversine)
Computes the great-circle distance between two latitude/longitude points using the haversine formula.
Initial bearing between two points
Computes the initial compass bearing (forward azimuth) from one latitude/longitude point toward another along the great circle.
Moon phase from a mean synodic month
Estimates the moon phase name and age in days for a given date using the mean synodic month from a cited reference new moon.
Solar declination from day of year
Estimates the sun's declination angle for a given day of the year using Cooper's formula.
Tide height by the rule of twelfths
Estimates the tide height at a query time between a known high and low tide using the traditional rule-of-twelfths approximation.

cooking

Baker's percentage
Converts a list of baker's percentages (relative to flour weight) into actual ingredient weights.
Brine solution by salt percent
Computes the salt weight needed for a brine at a given salt percentage of the water weight.
Cooking time scaling by weight
Estimates total cooking time from item weight using a stated minutes-per-unit-weight rule of thumb plus a fixed base time, both supplied as inputs.
Cups to grams for common ingredients
Converts a volume in US cups to a weight in grams for a small set of common cooking ingredients using cited density values.
Oven temperature conversion
Converts an oven temperature between Fahrenheit and Celsius, finds the nearest UK gas mark, and gives the standard fan-oven adjustment.
Recipe scaling
Scales a list of ingredient quantities from an original serving count to a desired serving count.

currency

Currency conversion at a stated reference rate.
Converts an amount between EUR and one other currency using a stated rate (units of that currency per 1 EUR), the date it applies to, and its cited source, all supplied by the visitor.
Currency cross rate
Computes the cross exchange rate between two currencies from their two given rates against a common base currency, and converts an amount.
Price with VAT or sales tax
Adds a tax rate to an exclusive price, or removes a tax rate from an inclusive price, given a stated tax percentage.
Unit price comparison
Computes the price per unit for two package sizes and reports which package is the better value.

dates

Add business days to a date
Adds (or subtracts) a count of Monday-to-Friday business days to a date, treating Saturday and Sunday as non-business days and excluding NO holidays.
Add days to a date
Adds (or subtracts, for a negative count) a whole number of days to a calendar date.
Age in years, months, and days
Computes exact calendar age (years, months, days) between a birth date and an as-of date.
Calendar quarter and fiscal year
Computes a date's calendar quarter and its fiscal quarter and fiscal year for a given fiscal-year start month.
Countdown to a date
Computes the whole number of days, and the equivalent weeks and days, from one date to another.
Date of Easter (Western, Gregorian)
Computes the date of Western (Gregorian calendar) Easter Sunday for a given year using the Meeus/Jones/Butcher algorithm.
Day of year and days remaining
Computes a date's ordinal position within its calendar year and how many days are left in that year.
Days between two dates
Counts the whole days between two calendar dates, inclusive or exclusive of both endpoints.
Is it a leap year?
Determines whether a given year is a leap year under the Gregorian calendar rule.
ISO week number
Computes the ISO 8601 week-numbering year and week number for a given date.
Julian Day Number of a civil date
Converts a proleptic Gregorian civil date to its Julian Day Number (JDN).
Weekday of a date
Computes the day of the week for any proleptic Gregorian calendar date.

finance

Amortization schedule row
Computes the interest, principal, and remaining balance for a single payment number of a fixed-payment amortizing loan.
Amortized loan payment
Computes the fixed monthly payment for a fully amortizing loan using the standard annuity payment formula.
APR to APY (effective annual rate)
Converts a nominal annual percentage rate compounded periodically into the effective annual percentage yield.
Break-even units
Computes the number of units a business must sell to cover fixed costs, given the unit price and unit variable cost.
Compound interest
Computes the final amount of a principal that compounds periodically at a fixed nominal annual rate.
Discount and markup
Applies a percentage discount or a percentage markup to a price and returns the new price and the dollar change.
Future value of an annuity
Computes the future value of a series of equal periodic payments, either an ordinary annuity or an annuity due.
Inflation-adjusted value (CPI method)
Converts a dollar amount from one period to another period's dollars using two Consumer Price Index values.
Percent change and CAGR
Computes the simple percent change between a starting and ending value, and the compound annual growth rate (CAGR) over a stated number of years.
Present value of a lump sum
Computes the present value of a single future cash amount, discounted at a given annual rate.
Rule of 72 and exact doubling time
Estimates the years to double an investment with the Rule of 72 approximation and computes the exact doubling time with logarithms.
Simple interest
Computes simple (non-compounding) interest and the total amount owed or earned on a principal over a term.
Tip and split a bill
Computes the tip amount, the total bill, and each person's even share when a bill is split among a number of people.
Total interest over a loan
Computes the total interest paid over the full life of a fixed-payment amortizing loan.

geometry

Circle circumference and area
Computes a circle's circumference and area from its radius or diameter.
Paint needed for a rectangular room
Computes the liters of paint needed to cover a rectangular room's walls, given openings, number of coats, and coverage per liter.
Right triangle side by the Pythagorean theorem
Computes the missing side of a right triangle (hypotenuse or a leg) given the other two sides.
Slope grade percent and angle from rise and run
Computes the percent grade and the angle from horizontal for a given rise and run.
Sphere and cylinder volume and surface area
Computes the volume and total surface area of a sphere or a right circular cylinder.
Triangle area by Heron's formula
Computes the area of a triangle from its three side lengths using Heron's formula.

health

Basal metabolic rate (Mifflin-St Jeor)
Estimates resting basal metabolic rate in kcal/day from sex, weight, height and age using the Mifflin-St Jeor equation.
BMI and WHO weight category
Computes body mass index from weight and height and reports the WHO adult weight category.
Body surface area (Mosteller formula)
Estimates body surface area in square meters from height and weight using the Mosteller formula.
Daily fluid estimate by weight (Holliday-Segar)
Estimates a general daily maintenance fluid volume from body weight using the Holliday-Segar rule of thumb.
Ideal body weight (Devine formula)
Estimates ideal body weight in kilograms from sex and height using the Devine formula.
Pediatric per-dose amount from mg/kg/day divided
Computes the per-dose amount when a total daily mg/kg/day dose is divided into a number of doses per day, general formula only.
Running pace and finish time
Computes finish time from distance and pace, and converts distance and pace between kilometers and miles using the exact international mile.
Target heart rate zones
Estimates a moderate-to-vigorous target heart rate zone using the percentage-of-max method, and also the Karvonen (heart rate reserve) method when resting heart rate is given.
Total daily energy expenditure from BMR and activity
Multiplies a basal metabolic rate by a cited activity factor to estimate total daily energy expenditure.
Weight-based dose (general formula)
Multiplies a body weight in kilograms by a per-kilogram dose to compute a total dose, general formula only, optionally capped at a maximum.

other

Credit-weighted GPA
Computes a credit-weighted grade point average from a list of letter grades and their credit hours on the standard 4.0 scale.
Dew point (Magnus formula)
Computes the dew point temperature from air temperature and relative humidity using the Magnus formula.
Heat index (US NWS Rothfusz regression)
Computes the heat index (apparent temperature) using the Rothfusz regression as used by the US National Weather Service.
ISBN-10 / ISBN-13 check digit
Validates an ISBN-10 or ISBN-13, or computes its check digit, per the ISBN standard.
Luhn check digit
Validates a number against the Luhn checksum, or computes the Luhn check digit to append to a number.
Number base conversion
Converts a number represented in one base (2 to 36) to its representation in another base.
Percent of a value, or percent change between two values
Computes either a percentage of a base value, or the percent change from an old value to a new value.
Pressure altitude from station pressure (ISA)
Converts a station barometric pressure to pressure altitude using the ICAO/NOAA International Standard Atmosphere barometric formula.
Reading time estimate
Estimates the time to read a passage from its word count and a chosen reading speed in words per minute.
Roman numeral conversion
Converts between Arabic numbers (1-3999) and Roman numerals using standard subtractive notation.
Solve a proportion a:b = c:x
Solves the missing fourth term of a proportion a:b = c:x.
Wind chill (US NWS 2001 formula)
Computes the wind chill temperature using the US National Weather Service's 2001 formula.

tax

FICA payroll tax, by stated table
Computes employee-side FICA tax (Social Security, Medicare, and Additional Medicare Tax) on a given amount of annual wages, using a stated, cited FICA table.
Marginal vs. effective tax rate, by tax year
Computes both the marginal tax rate (the rate on the last dollar earned) and the effective tax rate (total tax divided by taxable income) using the published IRS brackets for a chosen tax year.
Standard deduction vs. itemized, at a stated deduction amount
Compares a stated, cited standard deduction amount against a given itemized deduction total and reports which is larger.
US federal income tax, by tax year
Computes US federal income tax owed on taxable income using the published IRS tax rate table for a chosen tax year and filing status.

timezones

Convert a time between fixed UTC offsets
Converts a wall-clock time and date from one fixed UTC offset to another, handling the date rollover if any.
Flight duration across time zones
Computes elapsed travel time from a departure local date/time/offset to an arrival local date/time/offset.
Meeting time across three fixed offsets
Converts a single UTC date and time into local wall-clock times at three fixed UTC offsets, noting any date shift.
US daylight saving time in effect?
Determines whether a given date falls within US daylight saving time under the federal rule, and reports that year's transition dates.

units

Angle conversion
Converts a plane angle between degree, radian, gradian, arcminute, and arcsecond per the BIPM SI Brochure definitions.
Area conversion
Converts an area between metric and US customary units using exact square-meter equivalents.
Data size conversion
Converts a digital storage quantity between bit, byte, decimal (KB/MB/GB/TB) and binary (KiB/MiB/GiB/TiB) units per IEC 80000-13.
Energy conversion
Converts an energy quantity between J, kJ, kWh, cal, kcal, BTU, and Wh using exact NIST SP 811 joule-equivalents.
Fuel economy conversion
Converts fuel economy between mpg (US), mpg (UK), L/100km, and km/L, correctly inverting the L/100km reciprocal rate.
Length conversion
Converts a length between metric and US/imperial units using exact NIST SP 811 meter-equivalents.
Mass conversion
Converts a mass between metric and avoirdupois units using exact NIST SP 811 kilogram-equivalents.
Power conversion
Converts power between W, kW, mechanical hp, metric hp, and BTU/h using exact NIST SP 811 watt-equivalents.
Pressure conversion
Converts a pressure between Pa, kPa, bar, atm, psi, mmHg, and inHg using exact NIST SP 811 pascal-equivalents.
Speed conversion
Converts a speed between m/s, km/h, mph, knots, and ft/s using exact NIST SP 811 length and time definitions.
Temperature conversion
Converts a temperature between Celsius, Fahrenheit, Kelvin, and Rankine using the exact NIST SP 811 defining formulas.
Volume conversion
Converts a volume between metric units and US customary or UK imperial volume units.