Molten-glass batch model

OSRS Seaweed Calculator

Plan giant seaweed and sand batches with the common 1.3 expected molten-glass yield from Superglass Make.

Set activity assumptions

Giant seaweed

Buckets of sand

Glass price

Seaweed price

Sand price

Estimated molten glass

Secondary output: 1,184.

How it works

This page models the material side of a Superglass Make batch: expected glass from a pairing of giant seaweed and sand, valued against the input prices.

Spell mechanics the model assumes

Superglass Make is a Lunar spellbook spell needing 77 Magic and Lunar Diplomacy; each cast consumes 10 air, 6 fire and 2 astral runes for 78 Magic experience and processes the seaweed and sand held in your inventory. One giant seaweed substitutes for six ordinary seaweed, so base capacity is the smaller of six times your giant seaweed and your bucket count. The spell then adds bonus glass; the 1.3 multiplier used here is the common planning expectation, floored to whole glass.

Matching seaweed to sand

Giant seaweed	Matching buckets of sand	Base capacity	Expected glass at ×1.3
1	6	6	7
2	12	12	15
3	18	18	23
4	24	24	31
5	30	30	39

Keep the furnace route in view: one bucket of sand plus soda ash makes one molten glass for 20 Crafting experience, with no Magic requirement, runes or bonus.

Interpretation thresholds

Cost per expected glass decides a batch, not the headline yield. With the page defaults — two giant seaweed at 50 gp and twelve buckets of sand at 18 gp — the batch costs 316 gp for an expected 15 glass, so break-even is about 21 gp per molten glass. Sand is roughly 68% of that cost, so a sand price change moves break-even about twice as far as the same percentage change in seaweed price. Then add rune cost, which the material margin excludes, and treat 1.3 as a long-run average.

\text{expected glass} = \left\lfloor \min(6 \times \text{giant seaweed},\ \text{sand}) \times 1.3 \right\rfloor

Inputs are kept at full precision. Discrete counts round up when a partial action cannot complete the goal; probabilities and rates keep their fractional meaning.

Worked example

Two giant seaweed paired with 12 buckets of sand have a base capacity of 12 glass and an expected displayed yield of 15 after the 1.3 multiplier and flooring. Second worked example: four giant seaweed stand in for 24 seaweed, so 24 buckets are the matching load and the expectation is ⌊24 × 1.3⌋ = 31 glass. Bringing only 18 buckets caps the base at 18 and the expectation at 23, wasting a whole giant seaweed of capacity.

Interpreting the result

Start by checking that each field describes the same scenario as the result: levels are visible base levels, bonuses are entered separately, costs are per unit, and a one-in-X rate means one divided by X on each eligible roll. The calculator updates immediately and writes the complete input state into the address bar. “Copy link” preserves those assumptions; “Copy result” copies a short summary rather than the entire method.

Do not treat a rounded count as an hourly rate. A required-action total says how many successful units complete the target under the entered reward. Banking, movement, failed attempts, animation timing, missed ticks and setup changes affect elapsed time. When time matters, measure a representative session with the same method and divide the required count by the observed successful actions per hour.

Economic outputs are arithmetic scenarios rather than live market quotations. Check current item values before buying supplies, include any outputs that can be sold, and consider limits or low-volume price movement. Probability outputs describe repeated independent trials; they do not promise that a result arrives at the displayed attempt count. The visible formula is the authority for what this page includes.

Read this as a planning estimate. Game updates, equipment effects, failures, travel, downtime and live prices can move a real session away from the mathematical result. Check the inputs against the account and use the output as a reproducible baseline.

Questions about OSRS Seaweed Calculator

Why does two seaweed use 12 sand?

Each giant seaweed represents six seaweed for the spell, so two pair with twelve buckets.

Is 1.3 glass guaranteed?

No. It is an expected multiplier over many casts; an individual batch varies.

Are rune costs included?

No. Add spell rune cost outside the shown material margin.

What do I need to cast Superglass Make?

The Lunar spellbook after Lunar Diplomacy, 77 Magic, and 10 air, 6 fire and 2 astral runes per cast for 78 Magic experience. Add the rune cost yourself.

Is Superglass Make better than a furnace?

They answer different questions. A furnace turns one bucket of sand plus soda ash into one glass for 20 Crafting experience; the spell needs runes and seaweed but returns more glass per bucket.

What happens if I bring more sand than seaweed?

Base capacity is the smaller of six times your giant seaweed and your bucket count, so the surplus side is unused while the rune cost stays the same.

Sources

Mechanics and fixed tables were reviewed in 2026. Price-like inputs are user-controlled or approximate rather than live quotes. Source links name the public reference used for the page; the visible formula states the exact implementation.

Old School RuneScape Wiki — Superglass Make — Requirements, rune cost, experience per cast and bonus-glass behaviour, reviewed 2026.
Old School RuneScape Wiki — Giant seaweed — One giant seaweed substituting for six seaweed in the spell, reviewed 2026.
Old School RuneScape Wiki — Molten glass — Furnace route of one bucket of sand plus one soda ash for 20 Crafting experience, reviewed 2026.

Related calculators

Crafting skill calculatorTurn molten glass into a Crafting level plan with per-action experience.Magic skill calculatorCompare Magic training methods against the experience a cast returns.Herb run calculatorThe same expected-value discipline applied to a farming round.GE tax calculatorApply sale tax to the glass before treating the margin as profit.

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