Smart Calculators for the USA
Explore free, interactive planning tools for 401(k) retirement, Roth IRA, US mortgages, business days, work timesheets, US time zones, concrete in cubic yards, and sales taxes.
Duration, Time & Date Tools
Days & Business Days
Calculate exact days between dates, US working business days (excl. US Federal Holidays), and date arithmetic.
Age & Life Milestones
Exact chronological age and roadmap for US milestones (401k 59½, Medicare 65, Social Security 67 & 70).
Work Hours & Timesheet
Calculate shift hours, unpaid breaks, payroll decimal hours, and 40-hr weekly overtime wages.
US Time Zone Converter
Convert time between Eastern, Central, Mountain, Pacific, Alaska, and Hawaii with automatic DST.
Time Duration Calculator
Add and subtract time intervals in hours, minutes, and seconds, and convert to decimal intervals.
US Financial & Retirement Planning
401(k) Calculator
Plan your retirement nest egg with employer match, salary growth, and IRS annual limits.
Roth IRA Calculator
Estimate your 100% tax-free retirement fortune with $7,000/yr annual contributions.
US Mortgage Calculator
Estimate monthly payments (PITI) with Property Taxes, Home Insurance, and PMI.
Retirement Planner
Calculate your target nest egg, Social Security benefit offset, and retirement gap.
FIRE (4% Rule) Calculator
Determine your Financial Independence number and years to early retirement.
Monthly DCA / Index Fund
Model Dollar-Cost Averaging into S&P 500 index funds and ETF portfolios.
CD Rate Calculator
Calculate guaranteed interest and APY compounding on Certificates of Deposit.
Compound Interest
Calculate compounding returns with daily/monthly frequencies and recurring additions.
Simple Interest
Compute simple interest (I = P × r × t) for promissory notes and personal loans.
US Sales Tax Calculator
State-by-state combined sales tax rates with exclusive & inclusive pricing.
US Construction, Math & Unit Tools
Diagonal Calculator
Calculate diagonal for rectangles, TV screens, square layouts, and 3-4-5 carpentry in inches and feet.
Gallon to Liter Calculator
Convert US liquid gallons (3.785 L), dry gallons, imperial gallons, and fluid ounces with gas price comparisons.
Concrete Calculator
Calculate cubic yards (yd³), 80lb/60lb Quikrete bags, slabs, footings, sonotubes, and project costs.
Triangle Calculator
Solve right triangles, SSS Heron's formula, SAS trigonometry, perimeter, angles, and area in inches and feet.