Everyday calculators

Find calendar age in years, months and days, plus elapsed days between a birth date and a selected comparison date.

Add or subtract calendar intervals, compare dates, and count or move through business days using chosen workdays and holidays.

Count elapsed calendar or business days between dates, with an end-date option and custom working-day and holiday controls.

Find a date's weekday, day number within the year and ISO week, using Gregorian calendar and Monday-based ISO conventions.

Calculate work or activity hours between clock times, subtract a break and view decimal hours for same-day or overnight intervals.

Add and subtract durations, evaluate supported time expressions or shift a civil date and time by an entered duration.

Total dated or weekly shifts, unpaid breaks and estimated pay, with configurable overtime and clock-punch rounding.

Measure elapsed civil time between clock times or dated timestamps, with break subtraction and clear overnight assumptions.

Convert dates and times using named-zone daylight-saving rules or explicit fixed UTC offsets, with repeated-time handling.

Convert data units and estimate transfer time, website traffic or average bandwidth with explicit reporting periods and allowance formats.

Encode UTF-8 text as Base64 or decode Base64 locally in the browser, without treating the encoded output as encryption.

Calculate IPv4 or IPv6 subnet ranges from CIDR prefixes, or validate a contiguous IPv4 dotted mask and its address capacity.

Generate passwords locally with cryptographic randomness, chosen character classes and optional unique-character constraints.

Percent-encode or decode a UTF-8 URL component locally, keeping component encoding distinct from encrypting or validating a full URL.

Estimate a US bra starting size from underbust and bust measurements using a direct-underbust convention, with fit limits explained.

Split group expenses with multiple payers, equal or unequal shares, and exact rounded settlements. Find who owes whom for trips and shared bills.

Calculate the final exam score you need from your current grade, target grade, and final exam weight.

Estimate an 18-hole index from adjusted differentials, calculate a course handicap or derive a score differential from entered course data.

Calculate semester and cumulative GPA using course grades, credit hours, and your institution’s grading scale.

Calculate the future GPA needed to reach your cumulative GPA goal and compare scenarios for your remaining credits.

Calculate weighted or points-based grades, exclude ungraded work, and compare what-if scores.

Convert foot length to Mondopoint millimeters and an approximate US adult size using a stated allowance and sizing model.

Plan a bedtime or wake time from a chosen sleep duration, or explore illustrative cycle times with a sleep-onset allowance.

Calculate a tip from a chosen percentage and divide the bill plus tip evenly among a selected number of people.

Estimate room cooling needs, or compare steady heating loss and cooling heat gains using US county temperatures and assembly references.

Estimate concrete for slabs, columns, tubes, solid stairs or curb-and-gutter sections, with mixed units, allowance and volume-based pricing.

Estimate gravel volume, weight and cost for rectangular or circular beds, including bag counts from entered density and bag weight.

Estimate mulch volume and cost from bed dimensions or a known area, with depth and editable bulk-density assumptions.

Estimate roof surface from footprint, pitch or angle, then calculate allowance, area cost or whole material packages from coverage.

Estimate solar electricity savings, financing cash flow, and payback from system cost, generation, self-use, export rates, and your own tariff assumptions.

Calculate floor areas, borders and other supported shapes with mixed measurement units, repeated quantities and area-based costs.

Explore straight-stair geometry, standard or flush mounting and headroom using finished-floor dimensions and explicit layout assumptions.

Estimate tile quantities, boxes and cost using area or layout assumptions, with grout gaps and an allowance for cuts and waste.

Convert length, area, volume, mass, speed, energy, data and temperature units, with US, imperial and binary distinctions made explicit.

Find density from mass and volume, or solve for mass or volume using the labeled SI-unit relationship.

Calculate expenditure-based GDP or reconcile entered income components, capital consumption and statistical discrepancy to a domestic total.

Convert centimeters and feet/inches, or estimate adult height from parental measurements using the same mid-parental reference in either unit system.

Calculate mass from density and volume using the stated units, while distinguishing mass from gravitational weight.

Calculate molarity, solute mass or solution volume, and convert concentration units with explicit density for mass-fraction ppm or ppb.

Calculate molar mass and an element-by-element mass breakdown from a supported chemical formula and versioned atomic-mass data.

Convert integers and standard Roman numerals from 1 to 3,999, or express the components of a validated date in Roman notation.

Calculate speed, distance or travel time, including speed from independently selected distance units and an elapsed-duration input.

Convert mass units or calculate gravitational weight from mass and an entered local acceleration, keeping mass and force distinct.

Estimate dew point, relative humidity or air temperature with the liquid-water Magnus approximation and explicit input ranges.

Estimate NWS apparent heat from air temperature and humidity, or infer humidity from a supplied dew point.

Calculate National Weather Service wind chill for temperatures at or below 50°F and wind speeds above 3 mph.

Roll a selected number of dice with equally likely sides using cryptographic random selection, and view each roll and total.

Try a fictional name-match score for entertainment, with a repeatable result that makes no claim about relationship compatibility.

Estimate appliance energy use and cost from wattage, operating time and tariff, with an optional average-load factor.

Solve voltage, current, resistance and power from two supported known quantities in a DC or purely resistive model.

Find series or parallel resistance, decode supported color bands, or estimate conductor resistance from dimensions and conductivity.

Estimate DC or simplified AC voltage drop from conductor data, or convert AWG and kcmil sizes to nominal wire geometry.

Calculate power from torque and RPM, or explore empirical quarter-mile horsepower estimates from elapsed time or measured trap speed.

Compare EV and petrol ownership costs using purchase price, fuel or charging, mileage, maintenance, insurance, charging losses, and final resale values.

Estimate trip fuel and cost using metric, US or independently selected units for distance, fuel economy and pump price.

Measure observed fuel economy from distance and fuel used, or compare odometer readings and fuel cost with consistent fill-up assumptions.

Calculate power from torque or work, and convert mechanical, metric, electric and boiler horsepower with explicit unit definitions.

Find driving distance and estimated journey time between places or coordinates using OpenStreetMap roads.

Compare nominal tire dimensions and speedometer effects, or estimate the aspect ratio needed for a different rim at the same diameter.