Dates & days / 01
Add or subtract calendar days from a date
Move forward or backward by a whole-day offset, verify month and year crossings, and avoid confusing offsets with inclusive day numbers.
Read the workingsTHE EVERYDAY MATH WORKBENCH
Less guesswork.
More figured out.
A sale price. A date on the calendar. A measurement in unfamiliar units. Find your answer, and see how it adds up.
AI-generated conceptual workspace.
GOOD QUESTIONS. CLEAR WORKINGS.FIELD KIT / 001
Formulas, not black boxesInputs stay in your browserUS + metric measuresNo sign-up
A TOOL FOR THE TASK
What are you figuring out?
Start with your question. Choose a method.
Leave with an answer you can check.
TOOL / 01
Percentage calculator
Find a percentage, a share, a change, or a sale price.
Open calculator
TOOL / 02
Date calculator
Count calendar days, weekdays, or add days to a date.
Open calculator
TOOL / 03
Unit converter
Convert length, mass, volume, area, and temperature.
Open calculatorFree local calculators. Example inputs are illustrative; no taxes, holidays, or live rates are supplied.
START WITH SOMETHING FAMILIAR
Three everyday questions.
Illustrative examples.
Change the inputs in each calculator.
THE TALLY & MEASURE WAY
The answer is only
half the story.
01
Name the base.
Every percentage needs a whole. Every measure needs a unit.
02
See the method.
We show the formula and the assumptions behind each result.
03
Check the context.
Know where rounding, calendars, and conventions matter.
FROM THE FIELD NOTES
A small guide goes a long way.
Dates & days / 02
Counting days between dates: start with the convention
Choose elapsed days, inclusive dates, or weekdays, and understand the endpoint rules before using a calendar result.
Read the workings
Percentages / 03
Percentage calculations: choose the right whole
Learn when to multiply, divide, or compare values, with worked percentage examples and a checklist for choosing the right denominator.
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Percentages / 04
Percentage increase and decrease: use the original value
Calculate relative changes, understand asymmetric increases and decreases, and recognize when a zero or negative starting value needs another approach.
Read the workings
Units & measures / 05
Unit conversions: match the quantity before the number
Choose compatible units, cancel conversion factors correctly, and distinguish length, area, volume, mass, and temperature before converting.
Read the workings
Units & measures / 06
US cups, fluid ounces, gallons, and liters
Convert US customary liquid volumes to metric, distinguish cup definitions, and keep Imperial, dry, and mass measures out of liquid calculations.
Read the workingsTHREE WAYS TO EXPLORE
A reference for the everyday.
BEFORE YOU CALCULATE
Good to know.
Why can two date tools disagree?
They may use different endpoint conventions or holiday calendars. Compare those settings before comparing the totals.
Do converted units change measurement accuracy?
No. A precise conversion factor does not make an approximate reading exact. Keep precision appropriate to your original measurement.
Are these calculators free?
Yes. The local tools require no account or payment. This version has no advertising or paid upgrade.
Are my inputs sent anywhere?
The calculator code runs in your browser. We do not send calculator inputs to a server or store them in browser storage. Hosting infrastructure may log page requests; see Privacy.
Does the date tool exclude US holidays?
No. Calendar mode counts all days. Weekday mode removes only Saturdays and Sundays. Confirm deadlines with the organization that sets them.
Which gallon and cup do you use?
The converter uses US liquid gallons and US customary cups. These differ from Imperial gallons and nutrition-label metric cups.