Calculator Guides is a growing collection of worked examples that help you choose the right tool, check its assumptions and use its result. Each guide links to the live calculator so you can replace the example values with your own.
Browse the latest guides
- Power Bank Capacity: Compare Phone Charges, Runtime and Recharge TimeFollow one 37 Wh example through phone charges, device runtime and recharge time, with explicit assumptions and a sensitivity comparison.
- When Is a Bigger Pack Better Value? Unit Price, Discounts and WasteCompare pack prices, calculate a waste break-even point, and see how coupons and multipack quantities can change the better buy.
- Days Between Dates: Inclusive Counting, Weekdays and Leap DaysCheck Friday-to-Monday dates, leap days, same-day ranges and the difference between weekdays and working days.
- Batch Cost vs Unit Cost: Compare Two Order QuantitiesCompare 25 and 50 units with worked costs, goods discounts, fixed charges and a check for unusable output.
- From Script Words to Video Runtime: A Practical Timing PlanEstimate spoken time from a measured pace, then separately count pauses and non-speaking visuals without double counting.
- Weighted Grades vs Raw Marks: Choose the Right CalculationSee when to pool raw marks, when to use course weights, and how to calculate a required final exam score from the syllabus.
- Food Cost Percentage vs Menu Price: A Worked Restaurant ExampleKeep recipe cost, food cost percentage, gross margin and markup on the right bases, then compare a rounded selling price.
- How to Estimate Blanket Yarn From a Crochet SwatchMeasure an actual swatch, scale by area, add a transparent buffer and round to whole skeins without mistaking yarn weight for yardage.
- CCTV Storage Planning: From Bitrate to Retention DaysPlan camera storage using measured bitrate, recording schedule, camera count and retention; compare decimal TB with binary TiB before choosing capacity.
- Battery Backup Planning: Connect Ah, Wh, Load and RuntimeA worked battery-backup workflow shows how voltage, amp-hours, usable charge and efficiency change a runtime estimate, then checks inverter limits.
- Attendance Shortage vs Safe Bunks: Two Different QuestionsUse your held and attended classes to distinguish recovery classes from classes you can miss, with worked 75% examples and a future-block check.
Choose a guide by your question
Study and attendance
Do I need more classes, or can I miss one?
Why does my course grade differ from my marks percentage?
Battery and power
Do I need charge count, runtime or recharge time?
How do Ah and Wh translate into backup time?
Media and creator planning
How much camera storage does my retention target need?
How can I turn script words into a realistic runtime?
Shopping and unit prices
When does a bigger pack stop being better value?
Business costs
Which pricing target should I use: food cost, margin or markup?
Will a larger batch lower my cost per unit?
Craft projects
How much yarn should I buy from a measured swatch?
Calendar planning
Should I count both dates, and do weekdays include holidays?
Study & Grades: compare raw marks, weighted grades and attendance plans. Battery & Power: connect Ah, Wh and runtime. Media & Storage: plan camera storage and script timing. Business: distinguish food cost from margin and markup. Home & Craft: size a yarn purchase using a real swatch.
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