Bankrate
Mortgage amortization math, current 30-yr/15-yr fixed reference rates.
Trusted by 4.2M visitors monthly
The thirteen calculators you actually open at 11pm.
Mortgages, IRAs, percentages, and the grade you need on the final. Real formulas, audited monthly, free forever — built for the way real people actually do quick math.
13
Calculators · production
30+
State-level pages
99.97%
Math precision · audited
$1.24M
Sample IRA projection
The full calculator library
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13 tools · Finance · Academic · Specialty
322k / mo
Final Grade Calculator
Find the final exam score needed for your target course grade.
94.8% neededOpen
214k / mo
GPA Calculator
Estimate semester or cumulative GPA from credits and grades.
3.72/ 4.0Open
64k / mo
Snow Day Calculator
Estimate snow day odds from forecast and school conditions.
68% chanceOpen
198k / mo
Tip Calculator
Split a bill and choose a tip percentage.
$13.20· 18%Open
285k / mo
Mortgage Calculator
Estimate monthly payments from price, rate, and term.
$2,418/ moOpen
176k / mo
Loan Calculator
Calculate monthly payment and total interest.
$412/ moOpen
132k / mo
Compound Interest Calculator
Project savings growth over time.
$48,217· 10 yrOpen
142k / mo
Roth IRA Calculator
Estimate retirement account growth and contributions.
$1.24M· at 65Open
112k / mo
Sales Tax Calculator
Add or reverse sales tax from a purchase amount.
$108.25· 8.25%Open
94k / mo
Discount Calculator
Find sale price, savings, and percentage off.
$67.50· 25% offOpen
87k / mo
Concrete Calculator
Estimate concrete volume for slabs, footings, and posts.
2.74yd³Open
156k / mo
Percentage Increase Calculator
Find the percent increase between two values.
+25.0%Open
98k / mo
Percentage Decrease Calculator
Find the percent decrease between two values.
−18.0%Open
Methodology
Numbers you can show your accountant.
Every formula traces to a primary source — IRS publications, the Federal Reserve, Bankrate's amortization conventions. We update against rate changes within 24 hours of publication.
IRS Publication 590-A
Roth IRA contribution limits, MAGI phase-outs, distribution rules.
NerdWallet
Tip etiquette ranges and effective APR comparisons across loan products.
Federal Reserve / FRED
Historical CPI-U inflation series for compound interest projections.
College Board
GPA scale conventions and weighted AP/IB grading methodology.
Tax Foundation
State and local sales-tax rate tables, refreshed quarterly.
Popular by state
State defaults for mortgage and sales tax estimates.
Mortgage calculators
Sales tax calculators
Frequently asked questions
Everything you need to know to read the result with confidence.
What calculators are available on MathLab?+
MathLab includes focused tools for grades, GPA, tips, loans, mortgages, investing, shopping, home projects, and everyday percentages.
Are the calculators free to use?+
Yes. Every calculator is free to use without an account.
Can I use MathLab on a phone?+
Yes. The inputs, result panels, and supporting content are sized for quick mobile use.
Do calculators show their formulas?+
Yes. Each calculator shows the main formula or assumption used for the result.
Can I share a calculator with my inputs filled in?+
Yes. Open a calculator, change the inputs, and use the copy link button to share the current state.