Everyday calculators
Square Feet Calculator — Rooms & Floor Plans
Calculate square feet for one room or a full floor plan in exact feet and inches. Add rooms by floor, subtract excluded areas, and estimate materials and cost.
Alcohol Dilution Calculator — Water or Alcohol to Add
Calculate water or stronger alcohol to add, prepare an exact final volume, lower or raise ABV, blend two strengths, and convert U.S. proof.
Water Volume Calculator — Area, Depth & Gallons
Calculate US gallons from square feet and water depth, then plan pools, ponds, tanks, materials and volume conversions with editable examples.
Grade Calculator — Weighted Grades, Final Exam & GPA
Calculate weighted course grades, final exam targets, semester and cumulative GPA, or the GPA needed to reach a goal.
Age Calculator
Calculate exact calendar age in years, months and days, total elapsed days, hours and minutes, age on any date, and the next birthday.
Aquarium Volume Calculator — Water Level, Substrate & Sump
Measure tank water in six shapes, account for substrate and decor, add operating sump water, and compare your estimate with a measured fill.
Arrow Kinetic Energy Calculator — Momentum & Measurement Journal
Calculate arrow kinetic energy and momentum from finished arrow mass and speed. Keep repeated measurements and compare separate setups in a transparent journal.
Battery Runtime Calculator — Backup Load Planner
Plan how long a battery can power your outage loads. Switch appliances on or off, enter measured watts and duty cycles, and check the battery, goal and inverter together.
Box Cushion Calculator & Mixed Fabric Plan
Plan finished box cushion covers of different sizes on one fabric. Get cut pieces, zipper halves, a layout and an existing-cut check.
Candle Wax Calculator
Plan mixed candle sizes, weigh wax and fragrance, and work out complete batches from your ingredient stock.
Circle Skirt Calculator — Pattern & Fabric
Draft quarter to double-circle skirts with seam allowances, a waistband and fabric layout. Print an actual-size panel on A4 or Letter paper.
Continuous Bias Binding Calculator
Plan continuous bias tape from a fabric square. See full-width bands, discarded fabric and the square needed for your required length.
Cross Stitch Fabric Calculator — Size, Fit & Start Position
Size fabric for your cross stitch chart, compare counts, check an existing piece and see exactly where the design starts.
Depth of Field Calculator — Focus & Scene Planner
Check depth of field for your camera settings or choose a balanced focus distance and aperture to cover the near and far subjects in your scene.
Diagonal Quilt Backing Calculator
Plan a diagonal quilt backing with a rounded cut length, illustrated slide and seam, straight-panel comparison and printable cutting plan.
Drip Irrigation Calculator — Flow & Timer Comparison
Compare water delivered to different plant groups on one timer. Use rated emitter flow or a measured catch test, and see which groups receive more or less than their entered target.
Fabric Yardage & Cut Layout Calculator
Lay out rectangular fabric pieces with grain controls. Calculate yardage to buy, check an existing cut and print your cutting worksheet.
Free Date Calculator — Days Between Dates & Age Calculator
Calculate days between dates, add or subtract days, or find an exact age with weekend controls, clear steps, and instant visual results.
Generator Sizing Calculator — Running & Starting Watts
Size a generator from your appliance nameplate watts. Compare steady load, controlled motor starts and overlapping starts against both generator ratings.
Granny Square Blanket Calculator
Plan a blanket from measured motifs, edit its assembly map and calculate colour-specific yarn and whole balls after partial stock.
Headphone Power Calculator
Convert headphone sensitivity into required voltage, current and power. Compare headphones and explicit amplifier voltage and current limits.
IPv4 Subnet Calculator
Inspect IPv4 networks and plan aligned, nonoverlapping subnets for different host requirements. See exact address counts, /31 links, /32 routes and remaining CIDR blocks.
Knitting Increase & Decrease Calculator
Plan evenly spaced M1, KFB or K2tog in one knit row or round. Follow exact source stitches, step through the row and print your instructions.
LED Resistor Calculator
Choose a standard resistor for small DC LEDs, check a resistor you have and see current, power and wiring for series strings or parallel branches.
Macrame Cord Calculator — Sample, Cut & Spool Plan
Plan macrame cord lengths from your own knotted sample. Separate working and filler cords, add cut margin, and see an intact cutting plan for whole spools.
Ohm’s law
Find two unknown electrical quantities from any two measured values. Explore how resistance changes current and power with fixed voltage or current.
Parallel & Series Resistor Calculator — Build Mixed Circuits
Combine resistors in parallel, series or nested groups. Keep every original part and inspect its DC voltage, current and power.
Pizza Dough Calculator — Ingredients & Mixed Portions
Calculate flour, water and other ingredients for dough balls or mixed pizza and pan sizes. Keep the total dough mass and handling loss explicit.
Pool Alkalinity Calculator
Estimate sodium bicarbonate from measured pool alkalinity and your product label. Plan packages and recalculate from a fresh water test.
Pool Chlorine Calculator
Estimate a measured free-chlorine adjustment from your pool volume, test reading, chosen target and the exact strength unit on your product label.
Pool Heater Calculator
Plan pool heat-up time, the heater rating needed for a deadline, and optional gas or heat-pump cost using your measured water volume and cooldown.
Pool Pump Runtime Calculator — Flow, Hours & Cost
Plan daily pool-pump hours, circulated volume and energy from your actual flow and watts, with an optional second setting for a cleaner or other task.
Pool Salt Calculator
Work out how much pool salt to weigh, how many bags to buy and what remains. Preview salt levels and compare high-salt readings.
Pool Volume Calculator — Measure Gallons and Refill
Measure a pool’s inside dimensions, floor zones and waterline to estimate current gallons, full capacity and refill water.
Priming Sugar Calculator — Batch & Bottle Solution Doses
Plan priming sugar for beer or measured sugar-solution doses for mixed bottle sizes. Account for residual CO2, final solution volume and dilution.
Prop Slip Calculator — Measured Run Comparison
Calculate apparent propeller slip from pitch, gear ratio, RPM and measured speed. Keep multiple runs, compare setups and save your measurement record.
Quilt Backing Calculator — Yardage & Panel Layout
Compare horizontal and vertical backing layouts, seam placement and fabric yardage. Get a proportional diagram, cutting list and printable plan.
Quilt Binding Calculator — Strips & Fabric Yardage
Plan straight-grain binding strips, account for joins and end allowance, and buy the right fabric increment. Includes a visual cutting plan and printable list.
RC Time Constant Calculator — Charge, Discharge & Tolerances
Explore capacitor charge and discharge, time to a voltage threshold, and timing ranges from resistor and capacitor tolerances.
Screen Size Calculator
Find screen width and height from its diagonal, compare two screens at the same scale and see how much space a movie or image actually uses.
Serial Dilution Calculator — Transfer & Retained Volumes
Plan a dilution series with enough liquid left in every tube. Compare prepared and retained volumes, edit concentrations and save your transfer plan.
Soap & Lye Calculator — Build and Resize Your Recipe
Build a soap recipe with multiple oils, adjust SAP and lye purity, resize your batch and save a complete recipe file.
Spring Rate Calculator — Geometry & Measured Loads
Estimate a compression spring rate from round-wire geometry, or measure rate between two force and loaded-length readings. Compare the model and its provenance.
Time Calculator — Hours, Duration & Timesheet
Add or subtract time, find hours between clocks, total timesheet shifts and pay, or convert duration units with clear visual results.
Tip Calculator
Calculate restaurant tips before or after tax, split the bill equally or by custom shares, round the total, and see exactly what each person pays.
Titration Calculator — Concentration, Volume & Repeated Trials
Solve titration concentration or volume from a balanced reaction. Analyse repeated direct titrations with blank correction, dilution and a transparent report.
Yarn Calculator
Estimate blanket yarn from a weighed swatch, preview repeating stripes, subtract partial balls and print a colour-by-colour shopping list.
pH Calculator
Calculate ideal equilibrium pH for strong or weak acids and bases or conjugate buffers. Explore dilution with a curve that includes the contribution of water.
