Formula
- Use the units shown beside each field.
- Results update automatically whenever you change an input.
- Displayed values use up to four decimal places, or scientific notation for very small or large numbers. Calculations use standard floating-point arithmetic; exact integer and fraction tools identify their own precision rules.
- Purchase-cost comparison, not a lifecycle environmental assessment. Resale, borrowing and device energy are excluded.
Example Calculation
- Reader purchase cost: 120 currency
- Print book price: 15 currency/book
- E-book price: 9 currency/book
- Books to buy: 30
Reader 120 plus thirty e-books at 9 costs 390; print at 15 costs 450. Cost parity occurs at 20 books.
Frequently asked questions
How do I use this calculator?
Enter reader purchase cost, print book price, e-book price, books to buy. The result updates automatically. Use Reset to restore the example values.
What method does it use?
print=N × print price; digital=reader+N × ebook price; break-even=reader/(print−ebook) when saving is positive.. Purchase-cost comparison, not a lifecycle environmental assessment. Resale, borrowing and device energy are excluded.
Why might a rounded result differ?
The calculation keeps full numeric precision internally, then rounds the displayed result. Rounding intermediate steps by hand can produce a slightly different answer.
Are my inputs saved online?
No. This calculator processes your inputs in your browser. A recently used list stores only calculator names on this device, not your entered values.
Check the assumptions and units before using this result. Read about calculation methods.