Share ratio
A share ratio is the amount a BitTorrent client has uploaded divided by the amount it has downloaded, so a share ratio calculator is that one division and nothing else: put in the two sizes, and the answer is the figure your client displays.
A ratio of 1.00 means the two totals are equal. A ratio of 0.25 means a quarter as much went out as came in. There is no hidden weighting, no multiplication by anything, and no adjustment for how long a torrent stayed open.
Ratio calculator
The formula, and the two numbers it needs
The formula is uploaded divided by downloaded, with both quantities in the same unit. Megabytes over megabytes, gigabytes over gigabytes, bytes over bytes: the units cancel, which is why a ratio has no unit attached to it and is written as a bare decimal. Mixing units is the one way to get a wrong answer, so a torrent that has downloaded 700 MB and uploaded 1.4 GB has to have one side converted before the division happens.
Three details decide which numbers belong on each side of the line.
- Count only protocol data. Clients measure the payload they exchange with peers, not the tracker announces and handshakes around it, so the totals never match your router's traffic figures exactly.
- Count the whole history of that torrent, not the current session. Most clients keep both, and the all-time figure is the one that produces the ratio in the torrent list.
- Count a resumed torrent's earlier transfer too, if the client still has its resume data. A torrent removed and added again usually starts from zero downloaded, which produces an unexpectedly large ratio on the second run.
Working the number out from two sizes
A calculator on this page does the division for you. Enter the amount uploaded and the amount downloaded, choose the unit each is in, and it returns the share ratio, so you can check the figure a client is showing or work out what a torrent's ratio would become after a given amount of further uploading. It runs entirely in your browser and nothing is sent anywhere.
What each value on the scale actually means
Each value on the scale is a statement about two totals and nothing more. The table reads the arithmetic out loud, for a torrent whose payload is 1 GB.
| Ratio | What it says arithmetically | Uploaded, on a 1 GB torrent |
|---|---|---|
| 0.00 | Nothing has been uploaded at all | Nothing |
| 0.10 | A tenth as much has gone out as came in | 100 MB |
| 0.50 | Half as much has gone out as came in | 500 MB |
| 1.00 | The two totals are equal. One copy's worth has been given back | 1 GB |
| 2.00 | Twice as much has gone out as came in | 2 GB |
| Infinite, or a dash | Something was uploaded and nothing downloaded, so the division has no answer. This is what a torrent you created yourself shows | Any amount |
What counts as a good ratio is not a property of the arithmetic and this site does not set a number for it. The figure describes what your machine has done; the effect of a higher one is simply that more of the torrent existed in more places while you were connected, which is the mechanism The swarm describes.
Seed ratio, seed replacement ratio, and the swarm's own ratio
Seed ratio is the same number as share ratio, and clients use the two names interchangeably. The confusion worth clearing up is a different one: your share ratio and the swarm's seeder to leecher ratio are unrelated figures that both get called a ratio in ordinary conversation.
- Share ratio, or seed ratio
- Yours. Uploaded divided by downloaded, for one torrent or for everything the client has ever handled. It describes your machine.
- Seeder to leecher ratio
- The swarm's. Complete peers divided by incomplete peers on a given torrent. It describes how easy that torrent is to get, and it changes minute to minute as people come and go.
- Seed replacement ratio
- Not a BitTorrent term at all. The phrase belongs to agriculture, where it measures how much sown seed is bought fresh rather than saved. Searches for it land on torrent pages because of the word seed alone.
A download manager that fetches over HTTP has no ratio of any kind, because nothing is ever sent back. The number only exists because a BitTorrent transfer runs in both directions at once, which How a transfer works sets out in full.
Why upload is slower than download on most connections
Upload is slower than download on most home broadband because the line was designed that way. The A in ADSL stands for asymmetric, and cable and most fiber to the cabinet products inherit the same shape: a large downstream channel and a much smaller upstream one, on the assumption that households consume more than they send. Symmetric connections exist, mostly on fiber to the premises and business products, and there the two directions match.
This matters for a ratio because the ratio is a comparison of the two directions. On an asymmetric line, uploading as much as you downloaded takes considerably longer than the download took, and a torrent may need to stay open for many hours after the progress bar fills before the figure moves much. Neither direction is faster because it should be, and nothing in a client changes the shape of the line. What a client can change is how much of the available upstream it takes: leaving a small margin free keeps other things on the connection responsive, because a saturated upstream delays the acknowledgements that every download on the same line depends on. That is the one genuine case where uploading harder makes downloading feel worse.
Where the client keeps the figure
qBittorrent shows a ratio column in the main torrent list, per torrent, and a session and all time total in the status bar along the bottom. The same right click menu that sets a per torrent limit also resets a torrent's counters, and the option to stop or pause a torrent when it reaches a given ratio sits in the BitTorrent section of the preferences. Deluge and Transmission keep the same two views under their own labels.
Three things reset or distort the figure, and all three are ordinary: reinstalling the client, moving to a new machine without carrying the resume data across, and re-adding a torrent whose files are already complete, which registers as an upload with no matching download. A ratio is a running total kept by one program on one computer, not a score held anywhere else.