Daily Life

Shopping, cooking, DIY and household costs: the arithmetic you do on the back of a receipt, with the steps written out.

The home-improvement tools (paint, concrete, fabric, lawn) include sensible waste allowances and say when to buy extra.

19 tools · updated October 18, 2026

Percentage Calculator Solve the five common percentage questions: X% of Y, X as a percent of Y, increase, decrease, and the whole from a part. Double Percentage Calculator Apply two percentage changes in sequence and see the combined change, the error from simply adding them, and the change needed to undo both. Discount Calculator Find the sale price and saving from a percentage off, the real discount between two prices, or the original price before a markdown. Tip Calculator Calculate the tip and total on a bill and split it evenly, with each share rounded up to the cent so the bill is always covered. Recipe Converter Scale every ingredient in a recipe from its original yield to the number of servings you need, keeping the original units. Sales Tax Calculator Add US sales tax to a pre-tax price or back it out of a total, with statewide base rates for a dozen large states as presets. Unit Price Calculator Compare the price per unit of up to three package sizes, ranked from cheapest to most expensive with the premium over the best buy. Fuel Economy Calculator Calculate your measured fuel economy in US mpg, L/100 km, imperial mpg and km/L, plus fuel cost per mile and per kilometer. Paint Coverage Calculator Estimate how many gallons of paint the walls of a rectangular room need after subtracting doors and windows, for any number of coats. Fabric Yardage Calculator Estimate fabric yardage for common garments and home projects in 45- and 60-inch widths, rounded up to the next eighth of a yard. Concrete Calculator Calculate concrete volume for slabs and round columns in cubic feet and cubic yards, with a waste allowance and 40, 60 or 80 lb bag counts. Lawn Size Calculator Measure lawn area in square feet, square meters and acres from rectangles, circles and triangles, and estimate fertilizer and seed amounts. Cooking Conversion Calculator Convert kitchen volumes between spoons, cups and milliliters, and convert cups to grams or grams to cups for specific ingredients. Parking Meter Calculator Work out what a parking stay costs at an hourly rate with meter time steps, or how long a given amount of money buys. Laundry Cost Calculator Estimate the cost per load of home laundry from water, electricity and detergent, projected per week, month and year. Pet Age Calculator Convert a dog’s or cat’s age into human years with size-based dog charts and the AAHA/AAFP feline table, and show its veterinary life stage. Baby Formula Calculator Estimate how much formula a baby typically drinks per day and per bottle from age and weight, based on about 2.5 oz per pound of body weight. Plant Spacing Calculator Count how many plants fit in a rectangular bed at a given spacing on a square or triangular grid, with the area each plant gets. Commute Cost Calculator Calculate the yearly and monthly cost of a driving commute from fuel, wear, parking and tolls, plus the hours spent on the road.

Which everyday tool fits the question

One percentage or two in a row?

For a single question such as “what is 15% of 80” or “by how much did the price rise”, use the percentage calculator. When one change lands on top of another, the second acts on an already-changed number: 20% off followed by an extra 10% at the till is 28% off, not 30%. The double percentage calculator shows that gap, and the discount calculator works backward from a sale price to the original.

At the checkout and the restaurant

US shelf prices exclude sales tax, so the sales tax calculator adds your state’s base rate or the combined local rate you type in. The tip calculator splits a bill so the shares add up to the full amount, and the unit price calculator settles whether the big pack really is cheaper per ounce. Prices that include VAT are handled by the VAT calculator in the finance section.

Converting a recipe or scaling it?

These are different jobs. Changing cups to grams depends on the ingredient, because a cup of flour weighs far less than a cup of sugar; the cooking conversion tool carries ingredient densities for that. Cooking for eight instead of four is a scaling job for the recipe converter. Baking times and pan sizes do not scale in a straight line, so check those by eye.

Buying materials for a project

Measure first, then let the tool add the waste allowance: the paint calculator subtracts doors and windows and counts coats, the concrete calculator turns slab dimensions into cubic yards and bags, the fabric yardage estimator works from the project type and the width of the bolt, and the lawn size and plant spacing tools handle the garden. Buying a little extra in one go avoids color and batch differences later.

Running costs at home and on the road

Measure your own fuel economy from two fill-ups with the fuel economy calculator, then feed it into the commute cost calculator for a yearly figure. The parking meter and laundry cost tools price smaller routines. For the household itself, the pet age and baby formula calculators give general reference figures; a vet or pediatrician sets the real targets.