Utility Tools & Unit Converters
Convert units and handle everyday date, grade and percentage problems. The converters use standard NIST factors and show the factor applied, so you can verify the result. Calculations run in your browser.
Workflow Integration📊
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Unit conversion: pick the source and target units. The converters cover length, volume, pressure, time, power and speed, and the factor applied is shown next to the result.
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GPA and grades: enter course grades and credit hours to get a weighted GPA, and work out what grade you need in a remaining course to reach a target.
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Dates and age: calculate the exact time between two dates in years, months and days, with leap years and different month lengths handled correctly.
Exact Conversion Factors
Conversion errors in construction, engineering and trade usually come from rounded or mismatched factors. The converters use the exact definitions in NIST SP 811 and the SI Brochure (9th edition, 2019): 1 inch = 25.4 mm exactly, and 1 US gallon = 3.785411784 liters exactly. The US gallon is also about 20% smaller than the Imperial gallon (4.54609 liters), a frequent source of mistakes in fuel and volume figures. For grades, GPA is a weighted average: GPA = sum of (grade points × credit hours) divided by the sum of credit hours.
Technical Use Cases
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Construction and engineering: convert area and volume with exact factors and keep the original unit in your notes. 1 acre = 4,046.8564 m², and the US survey acre differs from it only by about 2 parts per million.
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GPA planning: with 15 credits at a 3.2 GPA, one more 3-credit course at 4.0 raises the 18-credit GPA to (15 × 3.2 + 3 × 4.0) / 18 = 3.33. High-credit courses move your average the most.
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Time zones: US daylight saving time starts on the second Sunday of March and ends on the first Sunday of November, while most of Europe changes on the last Sundays of March and October. In 2026 that left a gap from October 25 to November 1 when New York was 4 hours behind London instead of 5.
Questions and Answers
How does the GPA Calculator handle weighted credits?
It uses the standard weighted average: GPA = sum of (grade points × credit hours) divided by the sum of credit hours. On the common 4.0 scale, A = 4.0, B = 3.0, C = 2.0, D = 1.0 and F = 0.0. Some schools add plus and minus steps or give extra points to honors and AP courses (often a 5.0 scale), so check your school's policy. For three courses of 3, 4 and 3 credits graded A, B and A, the GPA is (4 × 3 + 3 × 4 + 4 × 3) / 10 = 3.6.
Are the unit converters accurate enough for professional or technical work?
Yes, within the precision you enter. The factors come from NIST SP 811 and the SI Brochure (9th edition, 2019). The inch is exactly 25.4 mm (international yard and pound agreement, 1959), and the US gallon is exactly 3.785411784 liters. The results are suitable for material estimates and technical notes. For contracts or regulated measurement, check the standard your industry specifies.
How does the Age and Date Duration tool handle leap years?
It applies the Gregorian rule: a year is a leap year if it is divisible by 4, except century years, which must be divisible by 400. So 2000 was a leap year and 1900 was not. The tool gives the duration in years, months and days. This helps with age checks, contract periods and any case where day precision matters.
Does the Time Zone tool account for Daylight Saving Time?
Yes, it applies regional DST rules on top of each zone's standard UTC offset. The rules differ by region: the US changes on the second Sunday of March and the first Sunday of November, and most of Europe on the last Sundays of March and October. For a few weeks each year the offset between New York and London changes from 5 to 4 hours. Check the exact date when scheduling around a change.
How does the Percentage Calculator handle reverse percentage problems?
It supports three directions: a percentage of a value (X% of Y), what percentage one value is of another, and the original value before a percentage change. For the original value, divide the final value by (1 - p/100) after a discount or by (1 + p/100) after an increase. If a price is $80 after a 20% discount, the original was 80 / 0.8 = $100, not 80 × 1.2 = $96. Applying the percentage to the discounted price is the most common error.
Why use these tools instead of a general search engine?
The converters show the exact factor they use, so you can verify it against NIST and cite it. They also accept several inputs at once, such as weighted GPA across many courses, and keep rounding consistent across all steps. When the method needs to be documented or audited, a tool that shows its working is more useful than a bare number.