All Utility Calculators
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Age Calculator
Exact age in years, months and days, total days lived and days until your next birthday.
Utility
GPA Calculator
Calculate your cumulative GPA from multiple subjects using letter grades and credit hours.
Utility
Time Zone Converter
Convert any date and time to multiple time zones simultaneously. DST-aware, all IANA zones supported.
Utility
Carbon Footprint Calculator
Estimate your annual CO₂ emissions from transport, home energy, diet and lifestyle. Compare to global averages.
Utility
Grade Calculator
Weighted course averages and final-exam-needed solver. US letter grade and UK degree class output.
Utility
Time Duration Calculator
Duration between two times, plus add and subtract hours, minutes and seconds. Decimal-hours output for timesheets.
Utility
Date Difference Calculator
Days, weeks, months and years between any two dates. Add or subtract days from a date and get the day of the week.
Utility
Square Footage Calculator
Floor or land area for rectangles, triangles, circles and trapezoids. Converts m², ft², yd², acres and hectares.
Utility
Concrete Calculator
Volume of concrete needed for slabs, footings, columns and post holes. Cubic metres, cubic yards and bag count.
Utility
Tile, Paint & Flooring Calculator
Tiles, litres of paint or boxes of flooring needed for any room — with built-in waste allowance.
Utility
Mulch & Topsoil Calculator
Cubic yards / m³ of mulch, topsoil, compost or gravel from area + depth. Bag count + weight.
Utility
Roof Pitch Calculator
Pitch ratio (x:12), angle in degrees and rafter length from rise + run.
Utility
Dog Age Calculator
Convert dog years to human years using AVMA logarithmic and AAHA size-adjusted scales.
Utility
Final Grade Calculator
What score do I need on my final exam to hit my target grade? Works for any weighting.
Utility
Solar Panel Payback Calculator
Cost, generation, savings, SEG income, payback period and 25-year ROI for residential PV.
Utility
Heat Pump vs Gas Boiler
15-year total cost of an air-source heat pump vs gas boiler. Includes BUS grant + CO₂ savings.
About Our Utility Calculators
All CalcWhizz utility calculators are free, accurate and GDPR compliant. Calculations run entirely in your browser — no personal data is stored or shared. Formulas are independently reviewed by qualified professionals and updated annually.
Important Note: This tool is intended to provide estimates and should not be used as a substitute for professional advice. Information generated by these calculators may be incomplete and does not account for all individual circumstances. Always seek the counsel of a certified expert (such as a financial advisor, healthcare provider, or licensed engineer) before taking action based on these results.