A quick exampleAn item costs 80 and sells for 100. Its profit is 20, margin is 20%, and markup is 25%.
For a target margin, divide cost by (1 − margin as a decimal). Include the costs relevant to your decision, and keep amounts in the same currency and reporting period.
A quick example60 × 40 × 30 cm ÷ 5,000 = 14.4 kg. If the box weighs 8 kg, its unrounded chargeable basis is 14.4 kg.
The divisor above is an editable example. Match units, divisor, dimension rounding, and weight rounding to your carrier and service. Compare each carton before multiplying by quantity. The workbench totals those carton-level results; it does not quote freight charges.
The loan calculator assumes a fixed rate and equal monthly principal-and-interest payments. The savings tools use a constant nominal annual rate and monthly compounding.
Monthly loan payment = P × r ÷ [1 − (1 + r)^(−n)]With no interest: monthly payment = P ÷ n
A quick exampleA 100,000 loan at 6% annual interest over 30 years has an estimated monthly principal-and-interest payment of 599.55.
P is the principal, r is the annual interest rate expressed as a decimal and divided by 12, and n is the number of months. Here “rate” means the interest rate used by the model, not a fee-inclusive APR. Loan results exclude fees, property taxes, and insurance. Savings results exclude taxes, fees, inflation, and changing returns. Contribution timing also changes compound-growth results.
A quick exampleA slab measuring 5m × 4m × 10cm has a 2m³ volume. A 10% allowance brings the estimate to 2.2m³.
Use the manufacturer’s mixed yield for concrete bags, coverage per litre for paint, and the supplier’s bulk density for gravel. Tiles and full boxes round upward separately. Choose a waste allowance for your actual layout; the defaults do not establish a structural specification or a universal ordering rule.
The standard and scientific calculators use mathematical postfix percentages: placing % after a number divides that number by 100.
10% = 0.1200 × 10% = 20200 × (1 + 10%) = 220
A quick example200 + 10% evaluates to 200.1. To increase 200 by 10%, enter 200 × (1 + 10%) or use the percentage tool.
Percentage change uses the original value as its base. Going from 80 to 100 is a 25% increase; going from 100 to 80 is a 20% decrease. A zero original value has no defined relative percentage change in this tool.
A calendar day count and an inclusive date count answer different questions. The date tools work with calendar dates, independent of daylight-saving clock changes.
Elapsed days = end date − start dateInclusive days = elapsed days + 1
A quick exampleOctober 1 to October 29, 2026 is 28 elapsed days, or 29 days when both dates are included.
Weekdays mean Monday through Friday and do not exclude public holidays. Age is counted in completed years, months, and days; end-of-month anniversaries clamp to the last valid date, so February 29 uses February 28 in non-leap years. Legal age conventions can differ. For overnight work, explicitly choose “following day”; work hours do not add overtime premiums.
Conversions use fixed unit definitions, but similarly named units can mean different things. The tool explanation identifies the conventions in use.
1 international inch = 2.54 centimetres1 avoirdupois pound = 0.45359237 kilograms1 GB = 1,000,000,000 bytes; 1 GiB = 1,073,741,824 bytes
A quick example0°C equals 32°F. Temperature scales include an offset, so that same formula must not be used to convert a temperature difference.
The length tool uses international feet and miles, and the weight tool uses avoirdupois pounds and ounces. Historical survey units and troy units are outside these tools. The temperature converter handles absolute temperatures. Storage units distinguish decimal prefixes from binary prefixes, and lowercase b means bits while uppercase B means bytes.