Online Calculators & Tools

Adds up a tow the way the invoice does: hook-up fee, billable miles, after-hours and winch-out surcharges, storage and tax, from the rates you were quoted.

Gives the tangent line to a curve at a point, the normal line through the same point, and the linear approximation with the error it makes nearby.

Finds the rule behind a list of numbers, arithmetic, geometric, quadratic or Fibonacci style, then gives the nth term, the sum and the terms that come next.

Turns an efficiency rating into money: annual cooling cost at your own electricity rate, the saving from a higher rating, the payback on the price difference.

Works out engine RPM from road speed, tire size, gear ratio and final drive, and runs the same chain backwards for road speed or the axle ratio you need.

Works out the 500 m split, the finish time and the wattage for an erg piece, converting freely between any two of distance, time, split and power.

Estimates resting metabolic rate from lean body mass with the Katch-McArdle and Cunningham equations, so body composition drives the answer rather than height and age.

Turns a word count or a block of pasted text into a reading time at the speed you pick, and works backwards from a slot to the words that fit it.

Turns output and hours into productivity per hour and per worker-hour, measures how much of the available time was productive, and compares two periods.

Works out the pointwise mutual information of two events from their joint and marginal probabilities, or from raw counts and a corpus size, with PPMI and normalised PMI alongside.

Differentiates a polynomial in x, y and z with respect to any one of them, and returns the gradient, the second partials and the value of each partial at a point.

Picks the head size for a room, checks how many heads one outdoor unit will carry, and shows the short cycling penalty when an inverter head is too big.

Writes a 2x2 or 3x3 matrix as P D P inverse, with the eigenvalues, the eigenvectors that form P, the inverse and the check that the product returns A.

Factorises a 2x2, 3x3 or 4x4 matrix into L and U by Doolittle with partial pivoting, returning P, the permutation sign and the determinant.

Prices a land survey from your own per-acre or hourly rate, adjusted for survey type and terrain, with research, monuments, travel and plat recording as separate lines.

Shows how an indexed universal life policy turns an index move into a credited rate through participation, spread, cap and floor, and what the charges take.

Sums geometric, p-series, telescoping and arithmetico-geometric series, names the convergence test that settles each one, and shows a partial sum beside it.

Estimates what it would cost to rebuild your house from a local per square foot rate, and measures the dwelling coverage on your policy against it.

Works out what a renovation loan lends against the after-renovation value, and weighs the equity a project creates against the interest borrowing for it costs.

Converts a birth date to the Hebrew calendar and finds the Gregorian date the Hebrew birthday falls on in any year, with bar and bat mitzvah dates.

Builds an itemised cost for a garage from its size and your own rates: slab, framing, siding, roof, doors and wiring, attached or detached.

Costs a recipe per serving from ingredient quantities and pack prices, gives the food cost percentage against a menu price, and the price a target food cost needs.

Adds up a fantasy football stat line under your own league settings, with PPR, half PPR and standard presets and every point value as an editable field.

Evaluates a^(bx+c)+d at a point, solves it for x, turns a growth rate into a doubling time and half life, and fits a curve through two readings.

Works out the drop from a level line over any distance, how far away your horizon is, and how much of a distant object the curve hides from view.

Splits a fill between the E85 pump and the gasoline pump to hit a target ethanol content, and works out what a partial fill actually left in the tank.

Works out the vertical jump you need to touch the rim, hang on it or dunk with the ball clearing, and runs it backwards from a vertical you already have.

Works out joint compound by the pound and by the bucket for a board area, split across the tape, fill and finish coats, with the tape and screws to match.

Turns bust, waist and hip into a US, UK and EU dress size across the misses and plus ranges, and says which to take when the three disagree.

Builds f(g(x)) and g(f(x)) from two standard forms with your own coefficients, shows the substitution and evaluates both at any x you pick.

Adds up a day's caffeine from coffee, tea, cola and energy drinks against the 400 mg figure, and decays a dose over the hours to work out what is left.

Works out the BUN to creatinine ratio from conventional or SI laboratory units and places it in the low, normal, raised or markedly raised band.

Saddle height from your inseam by the LeMond and Hamley formulas, each named and kept separate, plus what a crank or shoe change does to it.

Works out how many balusters fill a railing opening, the even gap they leave and where to mark the rail, keeping every gap under the 4 inch sphere rule.

Finds the monthly payment on a loan amortised over a long schedule but due years earlier, and the lump balloon balance left owing on that date.

Works out the monthly payment on a balloon mortgage, the lump that falls due at five or seven years, and what refinancing that balance at a new rate would cost.

Works out how long an audiobook takes at a chosen playback speed, how much time that saves, and the speed you need to finish it by a deadline.

Finds the inverse sine of a value in degrees, radians and gradians, states the principal value range, and refuses anything outside -1 to 1 with a reason.

Converts an A1C percentage to estimated average glucose and back again, using the ADAG relation, with every result given in both mg/dL and mmol/L.

Projects a 403(b) balance at retirement from your salary, deferral rate, employer match and expected return, and applies the age 50 and 15-year service catch-ups.

Finds your western star sign from a birth date, with its element, quality, ruling planet and opposite sign, and says when a date sits on a boundary.

Converts VA to watts at a power factor and back again, with the reactive power in var, the phase angle and the current for a single or three phase supply.

Estimates how long a UPS or inverter battery bank holds a load, from the bank capacity in amp hours, the system voltage, inverter efficiency, depth of discharge and Peukert exponent.

Works out how a tire's gauge pressure changes with temperature or altitude, using the gas law and the standard atmosphere, in psi, bar and kPa.

Estimates a tattoo price from the shop hourly rate and minimum charge, the size of the design, and detail and placement factors you can change yourself.

Swimming pace per 100 and per 50 in both yards and metres, from a swim you have done or a target pace you mean to hold, with cumulative splits.

Turns a measured foot length in centimetres or inches into US men's, US women's, UK, EU and Mondopoint shoe sizes on a named conversion basis.

Turns a set's weight, reps and RPE into a percentage of your one rep max, and works the other way to give the weight for a target RPE.