Can I use a sub-category rank?

No. Use the main rank in Books or the Kindle Store. Sub-category ranks are relative to a few hundred or thousand titles and don't map to sales.

Amazon BSR to Sales Calculator

Q: How many books does a BSR of 100,000 sell?

On Amazon.com a Kindle eBook at #100,000 in the Kindle Store sells roughly one copy a day. A print book at #100,000 in Books sells roughly one copy every one to two days.

Enter a book's Best Sellers Rank to estimate how many copies it sells a day and a month, plus the revenue and KDP royalty that implies. Works for print books and Kindle eBooks on eight Amazon stores.

Best Sellers Rank Ranked in Amazon store Price (optional) Royalty per sale (optional)

–estimated sales per day

Sales per month–

Revenue per month–

Royalty per month–

Verdict–

Need the royalty per sale? Work it out with the KDP royalty calculator.

BSR to sales chart (Amazon.com)

Estimated copies sold at each rank. Print books sell about 55% as many copies as Kindle eBooks at the same rank, because the Books store moves fewer units.

BSR	Kindle / day	Kindle / month	Print / day	Print / month
#1	8,000	240,000	4,400	132,000
#10	3,000	90,000	1,650	49,500
#100	1,000	30,000	550	16,500
#500	247	7,400	136	4,070
#1,000	135	4,050	74	2,227
#2,000	76	2,279	42	1,254
#5,000	36	1,066	20	586
#10,000	20	600	11	330
#20,000	8.6	257	4.7	141
#50,000	2.8	84	1.5	46
#100,000	1.2	36	0.66	20
#200,000	0.70	21	0.38	12
#500,000	0.34	10	0.19	5.7
#1,000,000	0.20	6	0.11	3.3

How BSR turns into sales

Best Sellers Rank is Amazon's ranking of every product in a store by recent sales, updated roughly every hour. Amazon doesn't publish sales figures, but rank and sales follow a steady curve: the top ranks sell thousands a day, and sales fall off quickly further down.

This calculator fits that curve through commonly cited reference points for the US Kindle Store: about 1,000 sales a day at #100, 20 a day at #10,000 and 1.2 a day at #100,000. It interpolates on a log scale between them. The Books store uses the same curve × 0.55. Smaller Amazon stores are scaled down, for example amazon.co.uk and amazon.de × 0.3 and amazon.fr × 0.1.

Getting a useful estimate

Use the main rank. Take the rank in Books or Kindle Store, not a sub-category like "#3 in Gratitude Journals".
Check it on more than one day. A single sale can lift an obscure book 500,000 places for a few hours. Look at the rank on several days, or use a few books, before trusting a niche.
Kindle Unlimited borrows count. In the Kindle Store a KU borrow moves the rank like a sale, so a KU-heavy eBook may earn less than its rank suggests.
Treat it as a range. Seasonality, launches and ads all shift the curve. Read the number as "about 5 a day", not "exactly 5.2".

Questions

How many books does a BSR of 100,000 sell?

On Amazon.com, a Kindle eBook at #100,000 sells roughly one copy a day. A print book at #100,000 in Books sells roughly one copy every one to two days.

What is a good BSR for a book?

Under about #20,000 means roughly five or more sales a day. Under #100,000 means about a sale a day for a Kindle eBook, or one every other day for a print book. Above #500,000 a book sells only occasionally.

Where do I find a book's BSR?

On the Amazon product page, scroll to Product details and look for "Best Sellers Rank". The first number is the one to use.

How accurate is this?

It's the same kind of estimate KDP research tools use. It's good for comparing books and niches. For a single book, treat it as a ballpark: real sales can easily be half or double the estimate.