Réponses rapides de calcul

To find X% of a number, multiply the number by X and divide by 100. To find what percent A is of B, divide A by B and multiply by 100.

Subtract the original value from the new value, divide by the original value, and multiply by 100.

Find a common denominator, convert both fractions, then add the numerators. Simplify the result if possible.

Multiply the numerators together and multiply the denominators together. Simplify the result.

For rectangles, multiply length × width. For irregular shapes, divide into rectangles, calculate each, and add them together.

Divide square feet by 10.764 to get square meters, or multiply by 0.0929.

Multiply the bill amount by the tip percentage (as a decimal). For 20% tip on $50: $50 × 0.20 = $10 tip.

Add the total bill plus tip, then divide by the number of people.

Multiply the original price by the discount percentage, then subtract from the original price.

Divide miles driven by gallons of gas used.

Divide the price of gas by your MPG.

Specify a minimum and maximum value, then use a random number generator to pick a value in that range.

Divide the number of favorable outcomes by the total number of possible outcomes.

Trigonometric ratios. Sin = opposite/hypotenuse, Cos = adjacent/hypotenuse, Tan = opposite/adjacent.

Multiply or divide by the conversion factor. 1 mile = 1.609 km, 1 kg = 2.205 lbs, 1 gallon = 3.785 liters.

Multiply the price by the tax rate (as a decimal), then add to the original price.

Convert letter grades to points (A=4, B=3, etc), multiply by credit hours, divide total by total credits.

Weight each component by its percentage of the final grade, then add.

15% of 200 equals 30.

The square root of 144 is 12. (12 × 12 = 144)

2026 in Roman numerals is MMXXVI (M=1000, X=10, V=5, I=1).

25% of 80 equals 20.

10% of 500 equals 50.

Mean = sum ÷ count. Median = middle value when sorted. Mode = most frequent value.

Find the mean, subtract mean from each value, square the differences, find mean of squares, take square root.

30% off $150 is $45 discount. Sale price is $105.

The Greatest Common Factor (GCF) of 24 and 36 is 12.

The Least Common Multiple (LCM) of 4 and 6 is 12.

Slope = rise over run = (y2-y1)/(x2-x1). A slope of 2 means rise 2 for every 1 run.

2 to the power of 10 equals 1,024.

Log base 10 of 100 equals 2 (because 10² = 100).

For a right triangle: a² + b² = c². If two legs are 3 and 4, hypotenuse is 5.

Monthly payment depends on loan amount, interest rate, and term. The formula uses compound interest to determine fixed monthly payments.

Compound interest grows exponentially because interest earns interest. Use the compound interest formula with principal, rate, time, and compounding frequency.

Use the amortization formula. Monthly payment stays constant but proportion of principal vs interest changes over time.

Subtract the initial investment from the final value, divide by the initial investment, and multiply by 100.

Divide annual salary by 2,080 (52 weeks × 40 hours) for full-time hourly equivalent.

Multiply hourly rate by 2,080 hours (52 weeks × 40 hours) for annual equivalent.

Lease payment is based on depreciation (cap cost minus residual), plus rent charge (money factor × cap cost + residual).

Lenders typically use 28% of gross monthly income for housing costs (mortgage, taxes, insurance).

Divide past value by CPI then, multiply by CPI now to get equivalent purchasing power.

Add up all your assets (cash, investments, property) and subtract all your liabilities (debts, loans).

A common rule is to save 10-15% of income, aiming for 25× your annual expenses by retirement (4% withdrawal rule).

Higher payments = faster payoff. Use debt avalanche (highest interest first) or snowball (smallest balance first) methods.

Divide your goal by your monthly savings to find months needed. Account for interest earned.

US federal tax uses progressive brackets. Each income portion is taxed at its bracket rate.

Subtract federal tax, state tax, Social Security (6.2%), Medicare (1.45%), and deductions from gross pay.

At 6.5% interest for 30 years, a $300,000 mortgage costs about $1,896 per month (principal and interest only).

At 7% APR for 5 years, you'll pay about $4,700 in total interest on a $25,000 car loan.

$25 per hour equals $52,000 per year for full-time work (40 hours/week, 52 weeks).

15% tip on $80 is $12.00. The total bill would be $92.00.

At 7% annual return compounded yearly, $10,000 grows to about $19,672 in 10 years.

$30 per hour equals $62,400 per year for full-time work (40 hours/week, 52 weeks).

$20 per hour equals $41,600 per year for full-time work (40 hours/week, 52 weeks).

20% tip on $50 is $10.00. The total bill would be $60.00.

At 6.5% interest for 30 years, a $400,000 mortgage costs about $2,528 per month (principal and interest).

At 6.5% interest for 30 years, a $500,000 mortgage costs about $3,160 per month (principal and interest).

18% tip on $100 is $18.00. The total bill would be $118.00.

To save $50,000 in 5 years, save $833/month. In 3 years, save $1,389/month.

BMI equals weight in kilograms divided by height in meters squared. For imperial: multiply weight (lbs) by 703, then divide by height (inches) squared.

Underweight: <18.5, Normal: 18.5-24.9, Overweight: 25-29.9, Obese: 30+. BMI is a screening tool, not diagnostic.

BMR (Basal Metabolic Rate) estimates calories burned at rest. Multiply by activity factor for TDEE (total daily expenditure).

Total Daily Energy Expenditure - calories you burn per day including activity. BMR × activity multiplier.

Calculate TDEE first, then distribute calories among protein (4 cal/g), carbs (4 cal/g), and fat (9 cal/g) based on your goal.

General recommendation: 0.8g per kg body weight. Athletes/bodybuilders: 1.6-2.2g per kg.

The US Navy method uses circumference measurements (neck, waist, and hip for women) along with height to estimate body fat.

Each sleep cycle is approximately 90 minutes. Count backward from wake time in 90-minute increments, adding 15 minutes to fall asleep.

Ovulation typically occurs 14 days before the next period. For a 28-day cycle, that's around day 14.

Add 280 days (40 weeks) to the first day of your last menstrual period. This uses Naegele's Rule.

A healthy BMI is between 18.5 and 24.9. Below 18.5 is underweight, 25-29.9 is overweight, 30+ is obese.

A 180 lb man with moderate activity burns about 2,700 calories daily. To lose weight, eat 2,200. To gain, eat 3,200.

At 5'9" and 165 lbs, your BMI is 24.4. This is in the "Normal" weight category.

A 150 lb woman with moderate activity burns about 2,000 calories daily. To lose weight, eat 1,500.

A BMI of 30 or higher is considered obese. 30-34.9 is Class I obesity, 35-39.9 is Class II, 40+ is Class III.

To lose 1 pound per week, create a 500 calorie daily deficit. 500 × 7 = 3,500 calories = 1 lb.

For BMI 21.5 (middle of healthy range): 5'4" = 125 lbs, 5'7" = 145 lbs, 5'10" = 165 lbs, 6'0" = 180 lbs.

Drink half your body weight in ounces. A 160 lb person should drink 80 oz (10 cups) of water daily.

Calculate volume in cubic feet (L × W × D), then divide by 27 to get cubic yards. Add 10% for waste.

One 80-lb bag covers about 0.6 cubic feet. Divide total cubic feet by 0.6.

Board feet = (Thickness × Width × Length) / 144, where dimensions are in inches except length in feet.

Calculate wall area, subtract doors/windows, divide by 350 sq ft (one gallon coverage). Add 10% for primer.

Calculate floor area in sq ft, divide by tile size in sq ft, add 10% for waste and cuts.

Calculate area in sq ft, multiply by depth in feet, divide by 27 for cubic yards.

Calculate cubic yards like mulch, then multiply by 1.4 tons per cubic yard for weight.

Measure roof area in sq ft, divide by 100 (one square = 100 sq ft), multiply by pitch factor.

Calculate wall area, divide by 32 sq ft (4×8 sheet). Add 10% for waste.

Calculate wall/ceiling area, account for stud spacing. R-value depends on climate zone.

Divide fence length by post spacing (typically 6-8 feet), add 1 for end post, add corner posts.

Rectangular: L × W × avg depth × 7.5. Round: diameter² × depth × 5.9.

A 10x10 foot slab at 4 inches thick requires 1.23 cubic yards of concrete. Add 10% extra for waste.

A standard 4x4 fence post hole (10" diameter, 2ft deep) needs about 2 bags of 80-lb concrete mix.

One cubic yard of concrete covers 81 square feet at 4 inches thick.

Divide your roof area in square feet by 100. One roofing square equals 100 square feet.

A 12x12 room with 8ft ceilings needs about 1.5 gallons per coat. Two coats = 3 gallons.

A 10-inch diameter hole, 2 feet deep needs about 0.4 cubic feet or 2 bags of 80-lb concrete.

For a standard 16" on-center stud wall, divide wall length (in inches) by 16, add 1. Include top plate, bottom plate, and extras for corners.

Standard modular bricks: approximately 7 bricks per square foot including mortar joints.

You need 3 bundles of shingles per roofing square (100 sq ft). Divide roof area by 100, multiply by 3.

4 inches for patios and sidewalks. 6 inches for driveways. 4-6 inches for garage floors.

Subtract the earlier date from the later date to get the difference in days.

Subtract your birth date from today's date to get years, months, and days.

Add minutes, if over 60 convert to hours. Then add hours.

Add or subtract the hour difference between zones. EST is UTC-5, PST is UTC-8.

ISO week 1 is the first week with at least 4 days in January. Most years have 52 weeks, some have 53.

July 4, 1776 was a Thursday. The Declaration of Independence was signed on a Thursday.

Christmas 2026 is December 25, 2026. Count the days from today to December 25, 2026.

The week number depends on today's date. ISO weeks start on Monday, and week 1 contains January 4th.

Subtract the earlier date from the later date. Include or exclude endpoints based on your needs.

Calculate days since birth: your age in years × 365 + leap years + extra days.

Count weekdays (Mon-Fri) between dates, excluding weekends. Optionally exclude holidays too.

Easter 2026 falls on Sunday, April 5, 2026.

There are 52 weeks and 1 day in a regular year, or 52 weeks and 2 days in a leap year.