Everyday Tools
Age
today − birth date
Exact age in years, months, days, hours, minutes, and seconds from a birth date.
Calculate →Battery Life
t = C / I^k (Peukert)
Battery runtime from capacity, load current, and Peukert exponent.
Calculate →Board Feet
BF = T × W × L / 144 (inches)
Lumber board feet from thickness, width, and length for woodworking projects.
Calculate →Cat Age
Cat years → human years
Cat-to-human age conversion accounting for accelerated early-life development.
Calculate →Cloud Base
h = 125 · (T − Td) (m, °C)
Cloud base altitude from temperature and dew-point spread.
Calculate →Concrete Volume
V = L × W × T (slab) · cylinder · footing
Cubic yards of concrete needed for slabs, cylinders, footings, and stairs.
Calculate →Days Between Dates
Date_b − Date_a
Calendar days, weeks, months, and years between any two dates.
Calculate →Dog Age
Dog years → human years (breed-aware)
Breed-aware dog-to-human age conversion — small dogs age slower than large breeds in late life.
Calculate →Earned Value Management
CPI = BCWP / ACWP · SPI = BCWP / BCWS
Project earned-value metrics — CPI, SPI, cost variance, schedule variance, VAC.
Calculate →Gas Mileage
MPG = miles / gallons
Vehicle fuel economy in miles per gallon, kilometers per liter, or liters per 100 km.
Calculate →GPA
GPA = Σ(grade × credit) / Σcredit
Grade point average from course grades and credit hours on a 4.0 scale.
Calculate →Brinell Hardness Number
BHN = 2P / (πD(D − √(D² − d²)))
Brinell hardness number from load, indenter diameter, and indentation diameter.
Calculate →Lightning Distance
d = sound speed × Δt(flash → thunder)
Distance to a lightning strike from the flash-to-thunder time delay.
Calculate →Markup & Margin
Markup = (Price − Cost) / Cost · Margin = (Price − Cost) / Price
Convert between markup and margin and project sale price from cost.
Calculate →Overtime Pay Rate
OT = base × (1.5 / 2.0 / 3.0)
Time-and-a-half, double-time, and triple-time pay across regular, OT, and holiday hours.
Calculate →Paint Coverage
Gallons = wall area / coverage_rate × coats
Gallons of paint required for a room from wall area, coverage rate, and coats.
Calculate →Pay Raise
New = Old × (1 + raise%)
Pay raise dollar effect, percentage, and projected take-home from a hourly or salaried wage.
Calculate →Percent Change
% = (new − old) / old × 100
Percent increase or decrease between two values.
Calculate →Percent Difference
% = |A − B| / ((A + B) / 2) × 100
Symmetric percent difference between two equally-weighted measurements.
Calculate →Percent Error
% = |experimental − true| / true × 100
Percent error of an experimental value against a known true reference.
Calculate →Percent Off Sale
Sale = Price × (1 − discount%)
Final sale price after a percent-off discount and the implied savings.
Calculate →Percent Yield
% = actual / theoretical × 100
Reaction percent yield from actual product mass vs theoretical maximum.
Calculate →Relative Humidity
RH = P_actual / P_saturated × 100
Relative humidity from actual and saturation water-vapor pressures.
Calculate →Restaurant Dining Tip
Tip = bill × tip%
Tip amount and bill total at a given tip percentage, split among any number of diners.
Calculate →Risk Equations
Risk = Hazard × Exposure × Probability
Carcinogenic and non-carcinogenic risk from exposure point concentrations and intake.
Calculate →Snow
Δh_w = Δh_s × ρ_s / ρ_w
Snow-water equivalent from snow depth and snowpack density.
Calculate →Square Footage
A = L × W (rectangle, triangle, circle)
Floor area in square feet for rectangles, triangles, circles, and irregular rooms.
Calculate →Tile
Count = area / tile area × waste
Number of tiles needed for a floor or wall with a waste-allowance buffer.
Calculate →Time Duration
end time − start time
Elapsed time between two times in hours, minutes, and seconds — for time sheets and billing.
Calculate →Time Zone Converter
UTC ± offset
Convert any time between two time zones with DST handling.
Convert →Tire Size Comparison
D = rim + 2(W · AR / 25.4)
Compare overall diameter, circumference, and speedometer error between two tire sizes.
Calculate →Trailer Towing
Tongue weight, weight-distributing hitch
Trailer tongue weight, weight-distributing hitch loads, and capacity check.
Calculate →Everyday utility calculators for the things people search most: dog and cat age in human years (breed-aware), overtime pay (time-and-a-half, double-time, triple-time), pay raise, days between dates, snow melt depth, trailer weight-distribution hitch, percent change/difference/error/off/yield, restaurant tip, gas mileage, paint coverage, tile and concrete volume, square footage, time-zone conversion, and more.
Used by anyone who wants a quick, accurate answer to a daily life or work question without installing an app.
When to use these calculators
Use Overtime Pay to compute time-and-a-half and double-time on top of regular hours. Use Pay Raise to project the dollar effect of a percentage raise. Use Dog Age and Cat Age (breed-aware) for pet vet-visit planning. Use Days Between Dates for billing, project deadlines, or pregnancy/anniversary tracking. Use Snow to estimate snowmelt water-equivalent depth.
These cover the common 'how do I calculate X' questions that don't fit a math or finance category.
Frequently Asked Questions
- How accurate is the dog age calculator?
- The Dog Age calculator uses a breed-aware lifespan-scaling formula instead of the legacy 1-year-dog-equals-7-human-years myth. Small breeds age more slowly than large breeds in late life. Inputs are calendar age and breed size; outputs are human-equivalent age.
- How is double-time pay computed?
- Double-time is 2× the regular hourly rate, typically applied to hours over a daily or weekly threshold (California: hours over 12 in a day) or to hours worked on a holiday. The Overtime Pay calculator handles regular, time-and-a-half, double-time, and triple-time tiers with configurable thresholds.
- What does percent error vs percent difference compute?
- Percent error compares an experimental value against a known true value (|experimental − true| / true × 100). Percent difference compares two equally-weighted measurements with no 'true' reference (|A − B| / ((A + B) / 2) × 100). Use percent error when one value is reference; percent difference when comparing two measurements.