OSRS TFA Calculator
Your purple chance in The Fractured Archive (TFA) from your share of the damage, your team and deaths, the raids an Obligator takes, Orion and what a raid is worth.
Damage counts the minions too, and half of any Defence your special attacks take off. Freezing or stunning the zombies at Xarth adds to your share there. Their deaths are the rest of the team's together.
Your chance of each unique
One roll for the whole team, and the purple goes to one player drawn by contribution.
| Unique | A raid | On average | Half get it by | Sells for | Adds to a raid |
|---|
How long until it drops
Every team size, side by side
Each size with an even share of the damage and your deaths. Each team size has its own chance of a purple, from 1 in 16 for one or two players to 1 in 7.5 for 8.
| Players | Team purple | Your purple | 1 in | A raid is worth |
|---|
Your deaths, side by side
| Your deaths | Contribution | Team purple | Your purple | 1 in | A raid is worth |
|---|
The other rewards
Rolled for you alone on every raid that does not end in a cabbage, whatever your contribution.
The standard loot
| Item | A roll | Quantity | A roll gives |
|---|
How lucky you have been
Contribution comes from damage. Each of the four rooms gives the team 100 contribution and Ocellus 300, shared by each player's damage, and a death takes away a tenth of your even share. The team's chance of a purple is set by its size, from 1 in 16 alone or in a duo to 1 in 7.5 in a team of 8, and the purple is yours as often as your share of the 700. Loot is priced at what it sells for right now, after the 2% tax, and a desiccated page at the dearest page it can be made into. A purple replaces the standard loot for the player who gets it, and a raid's worth counts that. Orion, the folio, the fragments and clue scrolls cannot be sold, so they are counted and never priced. A player who does too little gets only a cabbage, with none of these. Figures checked against the OSRS Wiki on 11 November 2026.
How the purple chance works
The Fractured Archive (TFA) has five rooms: the Archive Guardian, one boss from each of the next three pairs, and Ocellus. The first four rooms give 100 contribution each and Ocellus gives 300, so a raid holds 700. Each room's share is split between the players by damage, minions included. A special attack that lowers a boss's Defence counts half the Defence it takes off, and freezing or stunning the zombies at Xarth adds to the share there. A death takes away 10% of your expected contribution, which is the 700 split evenly: 35 in a duo, 17.5 in a team of four.
At the end the team rolls once at a rate set by its size, and the purple goes to a player drawn by contribution, so a player's chance is the team's rate times their contribution over 700. A solo raid and a duo both roll 1 in 16, a team of three 1 in 12.5 and a team of eight 1 in 7.5. A solo player has the whole chance; in a duo an even share is half of it.
| Players | Team, 1 raid in | Each player, 1 raid in |
|---|---|---|
| Solo | 16 | 16 |
| 2 | 16 | 32 |
| 3 | 12.5 | 37.5 |
| 4 | 10.5 | 42 |
| 5 | 9.5 | 47.5 |
| 6 | 8.5 | 51 |
| 7 | 8 | 56 |
| 8 | 7.5 | 60 |
Which unique you get
The rondache is 5 purples in 15, Zorya's tome 4, the Horn of Bran 3, the Ascension crossbows 2 and the Obligator 1. An Obligator is 1 purple in 15, so a duo with no deaths sees one in 240 raids.
| Unique | Weight | A duo, 1 raid in |
|---|---|---|
| Rondache | 5 in 15 | 48 |
| Zorya's tome | 4 in 15 | 60 |
| Horn of Bran | 3 in 15 | 80 |
| Ascension crossbows | 2 in 15 | 120 |
| Obligator | 1 in 15 | 240 |
What the standard loot is
A player without the purple gets three rolls of 33 items, and the same item can come twice. Ascension shards are five times as likely as most items, and since 11 November each comes in a 20% larger amount, about 90 to 98 before the five-times roll. Each roll has a 1 in 51 chance of five times the quantity. The amounts do not change with your contribution or the team's size.
The other rewards
Every raid that does not end in a cabbage rolls for Orion at 1 in 750 and an elite clue at 1 in 10, 5% likelier with the Elite combat achievements. The archivist's folio is 1 in 15 until you own one. An elemental fragment is 1 in 14, always one you do not have yet, until you have all four.
TFA questions
Does a bigger team lower the chance? Not the team's, which rises with each player past two. Your own share is smaller: an even share in a team of eight is 1 in 60, against 1 in 37.5 in a trio and 1 in 32 in a duo.
How much does a death cost? A tenth of an even share: 35 contribution in a duo, 17.5 in a four. It lowers your own chance and the team's, but a teammate's death leaves your chance alone. The deaths table shows it.
Does doing more damage help? Yes. Your chance follows your contribution, and Ocellus alone is 300 of the 700, so the damage there counts three times a room's.
What about the other raids? The CoX calculator, the ToB calculator and the ToA calculator do the same for the Chambers of Xeric, the Theatre of Blood and the Tombs of Amascut.
Update history
Every change to this calculator
- Unique chances now follow the 11 November rates for each team size, elemental fragments drop at 1 in 14, and Ascension shards come in larger amounts.
- Calculator added