OSRS Seaweed Calculator
Giant seaweed, buckets of sand, astral runes, coins and hours to your Crafting goal with Superglass Make, with the spores to grow it and what your bank makes.
Set experience directly to plan past level 99, up to 200M.
To your Crafting goal
A new line starts when a better glass item opens up, or when the glass starts going in the bank.
| From | The glass becomes | Casts | Glass blown | Time |
|---|
What the whole plan takes
Your shopping list for the goal, what it costs, what the glass sells for and the other experience it brings.
Every way to cast it, side by side
One cast of each, with the glass blown into the best item you can make now.
| A cast of | Glass | XP | Costs | gp/XP | XP an hour |
|---|
Every glass item
What each item is worth with the cast you chose, its own 10 experience a bucket included.
| Item | Level | XP each | XP a seaweed | Sells for |
|---|
Growing the seaweed
| Compost | A spore gives | Spores | Runs | Farming XP |
|---|
What your bank makes
Type what you hold and see how far it goes from your current level.
Every figure is an average. The glass from a cast is random, so a real bank lands a little above or below. Supplies are priced at what they cost to buy right now and glass items at what they sell for after the 2% tax. A figure with a ~ is an estimate: the casts an hour when you stop to pick glass up, and what an unwatched patch loses to disease. Light orbs cannot be sold. Figures checked against the OSRS Wiki on 24 September 2026.
How giant seaweed turns into Crafting experience
Superglass Make turns every bucket of sand you carry into molten glass and pays 10 Crafting experience a bucket. A giant seaweed counts as six seaweed, so three of them and 18 buckets fill one cast. The spell needs 77 Magic, 61 Crafting and Lunar Diplomacy, and costs 2 astral, 6 fire and 10 air runes. Blowing the glass is where most of the experience comes from.
| A cast of | Sand | Glass | A bucket | Cast XP |
|---|---|---|---|---|
| 3 giant seaweed, glass picked up | 18 | 28.8 | 1.6 | 180 |
| 3 giant seaweed, glass left | 18 | 26.1 | 1.45 | 180 |
| 2 giant seaweed | 12 | 17.4 | 1.45 | 120 |
| 13 seaweed | 13 | 16.9 | 1.3 | 130 |
| 13 soda ash | 13 | 16.9 | 1.3 | 130 |
| 13 swamp weed | 13 | 16.9 | 1.3 | 130 |
With three giant seaweed the inventory overflows and some glass lands on the floor. Picking it up is worth 588 experience a seaweed as lantern lenses against 538.5 if you leave it, and 732 against 669 as empty light orbs. Leaving it is faster, so it wins when seaweed is easy to come by and time is not.
Saving glass for light orbs
An empty light orb is 70 experience at level 87, where a lantern lens is 55. A cast pays its experience whether or not you blow the glass, so you can stop blowing part of the way, bank everything, reach 87 on casts alone and turn the whole bank into orbs. It takes the fewest seaweed of any route to 99. The calculator finds the level to stop blowing at when you pick that setting.
Giant seaweed from one spore
A seaweed patch has three lives, and compost, supercompost and ultracompost add one, two and three. Each seaweed picked has a chance to cost no life, from 59% at level 1 to 82.4% at 99. Magic secateurs and the Farming cape do nothing underwater. An attas plant does. There are two patches under Fossil Island, a spore takes about 40 minutes to grow and needs 23 Farming.
| Farming | Keeps a life | None | Compost | Super | Ultra |
|---|---|---|---|---|---|
| Level 23 | 64.1% | 8.3 | 11.1 | 13.9 | 16.7 |
| Level 30 | 66.0% | 8.8 | 11.8 | 14.7 | 17.7 |
| Level 40 | 68.4% | 9.5 | 12.6 | 15.8 | 19.0 |
| Level 50 | 70.7% | 10.2 | 13.7 | 17.1 | 20.5 |
| Level 60 | 73.0% | 11.1 | 14.8 | 18.6 | 22.3 |
| Level 70 | 75.4% | 12.2 | 16.3 | 20.3 | 24.4 |
| Level 80 | 77.7% | 13.5 | 18.0 | 22.5 | 26.9 |
| Level 90 | 80.1% | 15.1 | 20.1 | 25.1 | 30.1 |
| Level 99 | 82.4% | 17.1 | 22.8 | 28.4 | 34.1 |
Where the spores and the sand come from
Spores float up while you swim around the underwater part of Fossil Island, drop from lobstrosities and ammonite crabs, and can be bought on the Grand Exchange. Mernia will watch a patch for 200 numulites. For sand, ironmen mine sandstone in the desert quarry and have Sandstorm grind it, and everyone else buys buckets.
Seaweed questions
Two giant seaweed or three? Three. Two and 12 buckets never overflow, but they make no more glass a bucket than three with the overflow left, and fewer casts fit in an hour.
Does ordinary seaweed work? Yes, 13 with 13 buckets, as do soda ash and swamp weed, at 1.3 glass a bucket.
What else can Crafting be trained on? The Crafting calculator has every other method priced the same way.
Update history
Every change to this calculator
- Corrected the disease chance on an unwatched patch: about 5% a growth stage with ultracompost, over four stages
- Calculator added