Free calculators and everyday utilities that run entirely in your browser — no accounts, no paywalls, no clutter. Every tool explains the formula behind it and walks through a real example, so you understand the number, not just see it.
What DTI Do You Need for a Car Loan?
How auto lenders read your debt-to-income ratio, the payment it leaves room for, and the car price that payment buys.
How Much House Can I Afford?
A step-by-step guide from income, debts and down payment to a realistic home price, with examples from $60k to $150k a year.
Hourly to Salary, With Overtime
Convert an hourly rate to a yearly income, add overtime, and estimate take-home pay.
Should You Pay Off Debt Before Buying a House?
A framework for deciding between paying down debt and growing your down payment.
You're Saving 20% of Your Paycheck — Now What?
A practical guide connecting your budget, savings goals, and retirement numbers into one plan.
Mortgage Calculator
Estimate your total monthly payment including principal, interest, taxes, insurance, and PMI.
How Much House Can I Afford?
Find a comfortable home price based on your income, debts, and down payment.
Rent vs Buy Calculator
Compare the true cost of renting and buying, including appreciation and your breakeven year.
Debt-to-Income (DTI) Ratio Calculator
Find the DTI ratio lenders use to decide how much you can borrow.
Credit Card Payoff Calculator
See how long it takes to pay off a balance, or what payment you need to hit your payoff goal.
Personal Loan Calculator
See your monthly payment, total interest, and full payoff breakdown for a personal loan.
Auto Loan Calculator
Estimate your monthly car payment, including sales tax, down payment, and trade-in.
Budget Calculator (50/30/20, 60/20/20, 40/30/20/10)
Split your monthly take-home pay into needs, wants, savings and optional giving with the budget rule that fits you.
Salary & Take-Home Pay Calculator
Turn a gross salary into an estimated net paycheck with your own deduction rates.
Paycheck & Overtime Calculator
Estimate your gross pay per paycheck, including regular and overtime hours.
Compound Interest Calculator
See how your savings or investments grow over time with regular contributions.
Investment Calculator
Project how an initial investment plus monthly contributions could grow over time at a given rate of return.
Savings Goal Calculator
Find out how long it will take to reach a savings goal based on your monthly contribution and interest rate.
Retirement & 401(k) Savings Calculator
See how your retirement savings could grow by retirement age based on contributions, employer match, and expected return.
Tip Calculator
Work out the tip, the total bill, and how much each person owes if you're splitting the check.
BMI Calculator
Find your Body Mass Index, WHO weight category, and healthy weight range in US or metric units.
Calorie Calculator
Find your daily calorie needs (TDEE) and a target for losing or gaining 0.5 to 2 lb a week.
Due Date Calculator
Estimate your due date from your last period, conception, IVF transfer, or an ultrasound, plus key pregnancy dates.
Percentage Calculator
Find a percentage of a number, work out a percent change, or reverse a discount.
GPA Calculator
Calculate your semester or cumulative GPA, with honors/AP weighting and the GPA you need to reach a goal.
Grade Calculator
Work out your weighted class grade, or find the score you need on the final exam for an A, B, C or D.
Date Calculator
Count the days or business days between two dates, or add and subtract days from a date.
Time Calculator
Find hours worked between two times, add or subtract time, or total several durations.
Age Calculator
Find your exact age in years, months, and days, the age gap between two people, and days until your next birthday.
Password Generator
Create a strong, random password with an entropy and crack-time estimate.
Random Number Generator
Generate random numbers in any range, one at a time or in a batch, with or without duplicates.
Unit & Currency Converter
Convert length, weight, temperature and volume, plus live currency exchange rates.
Every tool on this site runs in your browser. The numbers you type — a salary, a loan balance, a due date — are calculated on your own device and are never sent to us or saved anywhere. There is nothing to sign up for and nothing to install.
Each calculator page follows the same pattern: the tool first, then a plain-English explanation of the formula it uses, a worked example you can check by hand, the common mistakes people make with that calculation, and answers to the questions people ask most. We test the math against independent calculations and edge cases (leap years, daylight saving changes, very large ranges) before a page goes live, and we correct any error readers point out.
The finance tools are estimates for planning, not personalized financial, tax, or medical advice. Lenders, employers, and doctors may use rules that differ from the general formulas here, so treat the results as a starting point for a conversation with a professional who knows your situation. Questions or corrections are welcome at contact@mysmartfreetools.com — read more about us.