Free Online Calculator Suite — 10 Essential Calculators for Everyday Math
Updated May 5, 2026 · 9 min read
Written by Muhammad Abdullah Rauf · Founder, EverydayTools.pro
10 calculators covering the math problems people search for most — health, finance, and math. All free, browser-based, no account required.
Whether you are splitting a restaurant bill, verifying your overtime paycheck, checking if a sale is actually a good deal, or planning a fitness goal — there is a calculator for that. This guide covers the 10 most useful calculators, explains the formula behind each, and links directly to the free tool.
The 10 Essential Calculators
Calculates your BMI and places it in the WHO classification table (Underweight / Normal / Overweight / Obese). Supports metric (kg/cm) and imperial (lb/in) inputs. Shows BMI for all age groups.
Common uses:
- Health screenings
- Fitness goal tracking
- Medical form requirements
Handles 3 percentage question types: What is X% of Y? X is what percent of Y? and What is the percentage change from X to Y? No formula memorization needed.
Common uses:
- Discount calculations
- Grade percentages
- Tax and tip amounts
Enter the bill total, tip percentage, and number of people — get the tip amount, total bill, and per-person share instantly. Supports custom tip percentages for any service quality.
Common uses:
- Restaurant dining
- Hotel gratuity
- Bill splitting with friends
Enter original price and discount percentage to get the final sale price and dollar amount saved. Also works in reverse: enter original and sale price to find the discount percentage.
Common uses:
- Shopping sale prices
- Coupon stacking
- B2B pricing negotiations
Calculates regular pay, overtime pay (1.5× rate for hours over 40/week), and total gross earnings. Supports both hourly and salaried employee overtime calculations per US FLSA standards.
Common uses:
- Payroll verification
- Hourly wage planning
- Overtime budget estimation
Enter annual salary and work hours per week to get hourly, weekly, bi-weekly, and monthly rates. Adjusts for different work schedules (32, 40, 50 hours/week).
Common uses:
- Job offer comparison
- Freelance rate setting
- Consulting fee calculation
Computes total value and interest earned for any principal, interest rate, and compounding frequency (daily, monthly, quarterly, annual). Shows year-by-year growth table.
Common uses:
- Savings account projections
- Investment planning
- Loan interest estimation
Enter a list of numbers and get mean (arithmetic average), median (middle value), mode (most frequent value), and range instantly. Handles any number of values.
Common uses:
- Grade averaging
- Survey data analysis
- Sports statistics
Estimates your Total Daily Energy Expenditure (TDEE) using the Mifflin-St Jeor formula. Enter age, height, weight, sex, and activity level to get maintenance, deficit, and surplus calorie targets.
Common uses:
- Weight loss planning
- Muscle gain diets
- Macro tracking baseline
Converts letter grades to grade points, weights by credit hours, and computes cumulative GPA. Supports 4.0 and 4.33 scale systems. Add/remove courses dynamically.
Common uses:
- Semester GPA tracking
- Academic scholarship eligibility
- Graduate school application prep
Which Calculator Do You Need?
| Task | Calculator | Category |
|---|---|---|
| Find if I'm a healthy weight | BMI Calculator | Health |
| Calculate X% of a number | Percentage Calculator | Math |
| Split a restaurant bill | Tip Calculator | Finance |
| Find the price after a discount | Discount Calculator | Finance |
| Check my overtime pay | Overtime Pay Calculator | Finance |
| Convert salary to hourly rate | Salary to Hourly | Finance |
| Project investment growth | Compound Interest | Finance |
| Find the mean of a data set | Average Calculator | Math |
| Calculate daily calorie needs | Calorie Calculator | Health |
| Compute semester GPA | GPA Calculator | Education |
More Calculators
Looking for something more specific? Browse all 40+ free calculators including health, finance, math, and productivity tools.
Frequently Asked Questions
Are all these calculators free with no signup required?
Yes — every calculator listed is 100% free, requires no account, and has no usage limits. They run entirely in your browser. No data is sent to any server.
What is the BMI formula and what do the numbers mean?
BMI = weight(kg) / height(m)². WHO classification: Under 18.5 = Underweight, 18.5–24.9 = Normal weight, 25–29.9 = Overweight, 30+ = Obese. BMI is a screening tool, not a diagnostic — a high BMI can indicate excess body fat but doesn't account for muscle mass.
How do I calculate a percentage change?
Percentage change = ((New Value − Old Value) / |Old Value|) × 100. A positive result means an increase; negative means a decrease. Example: price went from $80 to $100 → ((100 − 80) / 80) × 100 = 25% increase. Use the Percentage Calculator to solve this without the formula.
What is compound interest and how is it different from simple interest?
Simple interest earns interest only on the principal. Compound interest earns interest on both the principal AND previously earned interest, causing exponential growth. Formula: A = P(1 + r/n)^(nt) where P = principal, r = annual rate, n = compounding periods per year, t = years. Daily compounding grows faster than monthly, which grows faster than annual.
How is overtime pay calculated under US law?
Under the Fair Labor Standards Act (FLSA), non-exempt employees must receive 1.5× their regular hourly rate for all hours worked over 40 in a workweek. Some states (like California) also require daily overtime for hours over 8 in a day. Overtime Pay = Regular Hours × Rate + Overtime Hours × (Rate × 1.5).