Power Bank Capacity: Compare Phone Charges, Runtime and Recharge Time
Follow one 37 Wh example through phone charges, device runtime and recharge time, with explicit assumptions and a sensitivity comparison.
Category: Calculator Guides
When Is a Bigger Pack Better Value? Unit Price, Discounts and Waste
Compare 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 Days
Check 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 Quantities
Compare 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 Plan
Estimate 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 Calculation
See 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 Example
Keep 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 Swatch
Measure 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 Days
Plan 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 Runtime
A worked battery-backup workflow shows how voltage, amp-hours, usable charge and efficiency change a runtime estimate, then checks inverter limits.