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Specialty calculators
Specialty calculators
The arithmetic the calendar and a craft ask for over and over, in seventeen areas. Each one works in whichever units you already have, and every answer shows the working underneath it.
Date calculators
Days between dates, week numbers, working days, age, calendars and Easter.
- Days between two dates Days, weeks, months and seconds between two dates.
- Add to or subtract from a date The date a number of days, weeks, months or years away.
- Week number and day of the year ISO week number, day of the year, and the date as a number.
- Working days between two dates Business days between two dates, net of weekends and holidays.
- Add working days to a date The date a number of business days from now.
- Age calculator Exact age, the next birthday and the milestones of a life.
- Calendar converter The same date in the Hebrew, Islamic, Chinese and nine other calendars.
- Easter date calculator Western and Orthodox Easter, and the feasts that follow them.
Time calculators
Hours between times, timesheets, time zones, Unix timestamps and sleep cycles.
- Hours between two times Hours, minutes and seconds between two times of day.
- Add or subtract time The time of day after adding or taking away hours and minutes.
- Weekly timesheet Hours worked in a week, overtime and gross pay.
- Time zone converter The same moment in another time zone, daylight saving included.
- Unix timestamp converter Unix time and a dozen other epoch counters, to a date and back.
- Sleep cycle calculator Bedtimes and wake-up times in whole sleep cycles.
Home brewing and fermentation
ABV, IBU, priming sugar, mash water, pitch rates and blending.
- ABV from gravity readings Alcohol, attenuation and calories from an original and a final gravity.
- Hydrometer temperature correction The gravity a reading would have shown at the calibration temperature.
- IBU from a hop schedule Tinseth bitterness for a whole hop schedule, addition by addition.
- Priming sugar Priming sugar for a target carbonation, allowing for residual CO2.
- Mash and sparge water Mash, sparge, pre-boil and post-boil volumes from the batch size.
- Yeast pitch rate Cells, packs, dry yeast or slurry for a batch at a given pitch rate.
- Dilution and blending Gravity and ABV of a blend, and water to reach a target gravity.
Specialty coffee
Brew ratios, extraction yield, espresso, batch brewing and brew water.
- Brew ratio Ratios between dose, water and the beverage that reaches the cup.
- Extraction yield from TDS Extraction yield, solids and strength from a refractometer reading.
- Espresso dose, yield and time Brew ratio, flow rate and target yield for an espresso shot.
- Batch brewing Dose and water for a batch of a given beverage volume.
- Brew water from concentrates Millilitres of mineral stock for a target hardness and alkalinity.
- Bloom and pour schedule Bloom water and a pour-by-pour schedule with running totals.
3D printing
Filament cost, spool remaining, shrinkage, layer heights, flow and resin.
- Filament cost per print Material and electricity cost for one print, and prints per spool.
- Filament left on a spool Weight and length left on a spool from a caliper measurement.
- Shrinkage compensation Model dimension and scale factor to land on a finished size.
- Layer height and nozzle Layer counts and the usable layer range for a nozzle.
- Flow and extrusion multiplier Flow correction from a test wall, plus volumetric flow and speed limits.
- Resin volume and cost Resin volume, weight and cost per print, and copies per bottle.
- Infill weight Weight, filament length and cost from model volume and infill.
Photography and video
Depth of field, exposure equivalence, ND filters, time-lapse and storage.
- Depth of field and hyperfocal distance Near and far limits, total depth of field and hyperfocal distance.
- Exposure equivalence Equivalent exposures across ISO, aperture and shutter, with EV.
- ND filter exposure times Long exposure times for ND filters, in hours, minutes and seconds.
- Time-lapse interval and clip length Frames, clip length, shooting time and card space for a time-lapse.
- Crop factor and angle of view Equivalent focal length, equivalent aperture and angles of view.
- Card space from bitrate Card and disk space from bitrate, duration and camera count.
Astronomy and astrophotography
Magnification, focal ratio, pixel scale, star trailing, dew heaters and integration.
- Magnification and true field of view Magnification, true field, exit pupil and useful power range.
- Focal ratio and resolving power Focal ratio, resolving limits, limiting magnitude and light grasp.
- Pixel scale and sensor matching Arcseconds per pixel, field of view and sampling against the seeing.
- Maximum exposure before trailing Longest untracked exposure by NPF, 500 and 400, with sky drift.
- Dew heater wattage Heater power, current and battery drain for a dew strap.
- Integration time Total integration, elapsed time, SNR gain and nights to a target.
Cycling
Gear inches, cadence and speed, climbing power, tyre pressure and spoke length.
- Gear inches and development Gear inches, development and gain ratio for one gear combination.
- Cadence and speed across a cassette Speed, gear inches and development for every sprocket at one cadence.
- Gradient and climbing power Power, VAM and gradient for a climb at a given speed.
- Power to weight Watts per kilogram, and what it would take to reach a target.
- Spoke length Left and right spoke lengths for a given hub, rim and lacing.
- Tyre pressure Front and rear pressures from system weight and tyre width.
- Chain length Chain links and length from chainstay and the largest gears.
Textile crafts
Yardage, binding and backing, half-square triangles, gauge, yarn and shaping.
- Fabric yardage Fabric length for a set of pieces, with seams and shrinkage.
- Quilt binding and backing Binding strips, backing size and the yardage both take.
- Half-square triangles Cutting size and square count for half-square triangles.
- Knitting gauge and resizing Adjusted stitch and row counts for your gauge, and the error if you ignore it.
- Yarn substitution Skeins of a substitute yarn, and how its yardage compares.
- Increase and decrease spacing Shaping rows and the intervals to work them at, evenly spread.
Kitchen gardening and raised beds
Soil volume, compost C:N, plant spacing, fertiliser, drip lines and grow lights.
- Soil and compost for a raised bed Fill volume, mix, bags and delivered weight for a raised bed.
- Compost carbon to nitrogen Blended C:N for a heap, and the browns needed to correct it.
- Plant spacing and seeds Plants per bed, rows, seed count and area per plant.
- Fertiliser rates from an NPK label Product weight for a nitrogen rate, and what P and K come with it.
- Drip line flow and run time Run time, system flow and precipitation rate for a drip line.
- Grow-light DLI DLI from PPFD and hours, and what a target would need.
Beekeeping
Sugar syrup, honey weight, winter stores, varroa washes, forage and frames.
- Sugar syrup Sugar and water for a volume of syrup, at any ratio by weight.
- Honey volume to weight Weight, density, jars and water content for a volume of honey.
- Hive weight for overwintering Stores, total hive weight and the feed needed to reach a target.
- Varroa wash thresholds Mites per hundred bees, the seasonal threshold and the colony load.
- Forage area and colony density Forage area, colonies per square kilometre and nectar potential.
- Frame and box capacity Honey capacity, comb area and brood cells for a stack of boxes.
Off-grid power
Daily loads, battery banks, solar yield, charge time, inverters and cable size.
- Daily consumption Daily watt-hours and amp-hours from a list of appliances.
- Battery bank sizing Bank capacity in amp-hours and kilowatt-hours, and the modules it takes.
- Solar yield Daily yield, amp-hours and the array a daily load would need.
- Charge time Bulk and absorption time, amp-hours and energy to reach full.
- Inverter sizing Inverter rating, surge, DC current and fuse size.
- Cable size from voltage drop Cross-section and AWG for a run within an allowed voltage drop.
Hobby electronics
Ohm's law, LED resistors, dividers, RC filters, 555 timers and colour codes.
- Ohm's law Voltage, current, resistance and power from any two of them.
- LED series resistor Series resistor, nearest stocked value and the power it dissipates.
- Voltage divider Divider output, current, output impedance and the resistor for a target.
- RC filter cutoff Cutoff, time constant, rise time and the part for a target frequency.
- 555 timer Astable frequency and duty cycle, or monostable pulse width.
- PCB trace width Trace width to IPC-2221, with resistance, drop and power lost.
- Battery life Runtime from cell capacity, duty cycle and sleep current.
- Resistor colour code Resistor colour bands in both directions, with tolerance.
Home studio and live sound
Delay times, decibels, speaker impedance, port tuning, room modes and cable loss.
- Delay and reverb times from tempo Delay and reverb times in milliseconds for every note value.
- Decibel conversions dBu, dBV, gain factors and ratios as amplitude or power decibels.
- Speaker impedance Total impedance in series or parallel, and power per driver.
- Ported enclosure tuning Port length, area and air velocity for a box and a tuning.
- Room modes Axial modes, first tangential mode and Schroeder frequency.
- Audio file size Session size from sample rate, bit depth, tracks and duration.
- Speaker cable loss Cable resistance, power lost, damping factor and maximum run.
Car and motorcycle tuning
Gear ratios, speedometer error, displacement, injectors and tyre sizes.
- Gear ratios and speed Speed in every gear at a given engine speed, with overall ratios.
- Speedometer error from a tyre change Actual speed, error and diameter change after a tyre change.
- Displacement and compression ratio Displacement and compression ratio from the engine's own dimensions.
- Injector sizing Injector size for a power target, with a fuel-pressure correction.
- Fuel consumption and running cost l/100 km, mpg both ways, cost per kilometre and tank range.
- Tyre size comparison Diameters, sidewalls and revolutions for two tyre sizes compared.
DIY renovation takeoff
Tiles, paint, plasterboard, stairs, rafters, decking, fencing and bulk materials.
- Tiles and adhesive Tiles, boxes, adhesive and grout for an area, with waste.
- Paint quantity Paintable area, litres per coat and tins for a room.
- Plasterboard and compound Sheets, compound, tape, screws and studs for a wall area.
- Stair rise and run Risers, going, total run, stringer length and the comfort check.
- Roof pitch and rafter length Pitch in three notations, rafter and hip lengths, and roof area.
- Decking boards and joists Boards, linear metres, joists and screws for a deck.
- Fence posts and concrete Posts, bays, rails and the concrete the holes take.
- Mulch, gravel and bulk materials Volume, weight and bags of bulk material for an area and depth.
Print, zines and bookbinding
GSM and basis weights, spine width, imposition, bleed, roll length and envelopes.
- GSM and basis weights GSM against every US basis weight, with caliper and PPI.
- Spine width Spine width, text block and full cover width for a book.
- Imposition and signatures Signatures, sheets, blanks, creep and the page order per sheet.
- Bleed and safe margins Document size with bleed, safe area and cover spread width.
- Roll length by diameter Length, area, weight and percentage left on a roll.
- Ink coverage Total area coverage and ink used, per page and for the job.
- Envelope sizing The standard envelope a folded document needs, with a size table.
These are planning figures, not a substitute for a standard, a specification or a professional. Check anything that matters against the source your trade actually works to.