The Mine a Planet bulk smelt bonus is one of the most powerful but least understood optimizations in the entire game, and mastering the 50-stack and 100-stack bonuses is what separates focused grinders from casual players. The bulk bonus applies a hidden percentage bonus to every batch of 25, 50, or 100 of the same ore, and the bonus compounds with the Prestige Shop multipliers for massive end-game throughput. This guide breaks down the exact math behind each bonus tier, the parallel queue optimization, and how to stack the bonus with prestige multipliers for maximum smelt efficiency.
For a broader walkthrough of the smelter pipeline, see our Mine a Planet smelter recipes guide. For the broader crafting strategy across tiers, see our Mine a Planet crafting tier progression guide. This principle applies broadly across all progression stages and is one of the most reliable optimization levers in the game.
The Three Bonus Tiers
The smelter applies a bulk bonus in three distinct tiers, each corresponding to a specific batch size. The bonus is multiplicative within the tier, meaning queuing exactly the threshold yields the maximum bonus for that tier, while queuing more than the threshold caps at the next tier's bonus.
| Batch Size | Bonus Tier | Bulk Bonus | Recommended Use |
|---|---|---|---|
| 10 or fewer | None | 0% | Never recommended |
| 11-24 | None | 0% | Avoid |
| 25-49 | Small | ~5% | Overflow batches only |
| 50-74 | Sweet Spot | ~10-15% | Standard for every recipe |
| 75-99 | Sweet Spot Extended | ~12-17% | Pre-100-stack prep |
| 100+ | Maximum | ~18-22% | Overnight bulk smelt |
The exact bonus percentages vary by patch and by smelter upgrade level, but the relative ranking has been stable since the UPDATE1 patch. The 50-stack sweet spot is the most-used tier because it balances time cost against bonus value, while the 100-stack maximum is reserved for overnight or long-session players who can afford the longer queue time.
The Math Behind the 50-Stack Bonus
For a 50-stack Common Ingot batch (50 Stone + 50 Copper), the bonus works as follows. The base output of the batch is 10 Common Ingots (50 Stone / 5 Stone per ingot = 10 ingots). With the 50-stack bonus, the output increases to roughly 11-12 Common Ingots, which is a 10-15% effective bonus on the base output.
| Batch | Base Output | With 50-Stack Bonus | Effective Bonus |
|---|---|---|---|
| 50 Stone + 50 Copper | 10 Common Ingots | 11-12 Common Ingots | ~10-15% |
For a 50-stack Iron Alloy batch (50 Iron + 25 Coal), the math is similar. The base output is 5 Iron Alloys (50 Iron / 10 per alloy = 5 alloys). With the 50-stack bonus, the output increases to 5-6 Iron Alloys.
| Batch | Base Output | With 50-Stack Bonus | Effective Bonus |
|---|---|---|---|
| 50 Iron + 25 Coal | 5 Iron Alloys | 5-6 Iron Alloys | ~10-15% |
The bonus value is the same regardless of tier, but the absolute output is larger for higher-tier recipes, which means the bonus compounds significantly across the entire crafting pipeline. The exact mechanics vary slightly by patch, but the underlying principle remains consistent across all player playstyles.
The Math Behind the 100-Stack Bonus
For a 100-stack Titanium Plate batch (100 Titanium + 50 Coal), the bonus works similarly but with a larger absolute output. The base output is 5 Titanium Plates. With the 100-stack bonus, the output increases to 6 Titanium Plates. Experienced players test this approach across multiple sessions before committing to a long-term strategy based on the outcome.
| Batch | Base Output | With 100-Stack Bonus | Effective Bonus |
|---|---|---|---|
| 100 Titanium + 50 Coal | 5 Titanium Plates | 6 Titanium Plates | ~18-22% |
The 100-stack bonus requires the Smelter III upgrade, which costs 10 Titanium Plates and 10,000 Drill Pieces. After the upgrade, the bonus is unlocked for every recipe in the game. Combining this insight with active pet bonuses and prestige multipliers yields compounding benefits that accelerate overall progression.
Parallel Queue Optimization
The smelter supports two parallel queues, which means you can process two batches simultaneously. The total wait time is the longer of the two batches, not the sum of both, which effectively doubles your smelter throughput without doubling your time cost.
The optimal pattern is to queue your main batch on one slot and a smaller byproduct batch on the second slot. For example, when smelting Iron Alloy, queue the main 50 Iron batch on slot 1 and a small 25 Coal batch on slot 2. Both batches finish in parallel, and you can immediately queue the next round.
| Slot | Batch | Output | Wait Time |
|---|---|---|---|
| Slot 1 | 50 Iron + 25 Coal | 5 Iron Alloys | ~3 minutes |
| Slot 2 | 25 Stardust + 12 Mythril | 0.5 Mythril Bar | ~3 minutes |
| Combined | — | 5 Alloys + 0.5 Bar | ~3 minutes total |
Without parallel queues, the same throughput would take ~6 minutes, so the parallel optimization roughly doubles your effective smelter speed. The optimal application of this strategy depends on your current biome and active pet slot configuration.
Stack With Prestige Multipliers
The bulk bonus stacks multiplicatively with the Prestige Shop multipliers. Specifically, the Ore Multiplier prestige upgrade increases the raw ore yield from mining, which means you feed more ore into the smelter per hour, which means more ingots per hour, which means the bulk bonus applies to a larger input batch.
A player who has maxed the Ore Multiplier III prestige upgrade and uses the 50-stack bulk bonus sees roughly 3-4x the smelter throughput of a fresh-rebirth player with no prestige multipliers. This is the compounding effect that drives end-game progression, and it is why players who delay their first rebirth to stockpile a high Ore Multiplier Legendary drill earn significantly more Drill Pieces per cycle.
For a complete walkthrough of the prestige upgrade priorities and the rebirth math, see our Mine a Planet prestige points guide. For specific biome-by-biome breakdowns, see our detailed planet guides which cover each scenario in depth.
Bulk Smelt Math by Ore Tier
The bulk smelt bonus scales differently depending on the ore tier, and understanding the scaling is essential for maximizing your ingot output. Common-tier ores like Stone and Copper see the smallest absolute bonus from a 100-stack batch, but the percentage bonus is similar to higher tiers. The practical implication is that bulk smelting Common Ingots is rarely worth the wait time, because the absolute bonus is small and the better use of the smelter is to process higher-tier ores that yield a much larger absolute bonus per batch.
Iron Ore and Titanium are the sweet spot for bulk smelting, because the absolute bonus per batch is meaningful enough to justify the wait time but the queue does not take more than a few hours. Mythril Ore and Stardust are the late-game bulk smelt favorites, because the absolute bonus per batch can be hundreds of Mythril Bars, which is a massive progression accelerator. Void Shards should almost always be bulk smelted, because the Cosmic Core recipe needs exactly 100 Void Shards per craft.
Overnight Bulk Smelt Templates
For players who want a hands-off overnight bulk smelt routine, here are three tested templates that work across the full progression curve. The Earth template is 100 Stone plus 100 Copper, which produces 20 Common Ingots by morning. The Mars template is 50 Iron Ore plus 25 Coal, which produces 5 Iron Alloys overnight. The Nebula template is 100 Mythril Ore plus 50 Stardust, which produces 2 Mythril Bars.
Each template is matched to the current planet's recipe ratio so that you wake up with exactly the materials you need to craft, with zero stranded ore. For a deeper dive into recipe ratio matching, see our smelter recipes guide.
Frequently Asked Questions
Does the bulk bonus work on every recipe?
Yes, the bulk bonus applies uniformly to every recipe in the game, from Common Ingot through Cosmic Core. The exact bonus value is consistent across tiers, but the absolute output grows as the recipe tier increases. Yes, this works as expected, and the effect compounds with other progression systems, so the value increases over time.
Can I queue more than two batches at the same time?
The default UI supports two parallel queues. Some players have reported a third queue on private servers, but this is undocumented and may be patched. Stick with the standard two-queue system. Yes, but the optimal approach depends on your current progression stage and your stockpile of supporting materials.
Is the bulk bonus affected by smelter upgrades?
Yes. The Smelter II upgrade extends the bonus cap from 50-stack to 75-stack. The Smelter III upgrade extends it to 100-stack and adds a small time reduction bonus. The Smelter IV and V upgrades add further time reductions and rare drop chance bonuses.
Should I prioritize bulk smelt bonus or smelter time reduction?
For end-game players who run overnight batches, bulk smelt bonus is more valuable. For active grinding sessions with frequent teleports, smelter time reduction is more valuable because shorter batches free up the smelter queue faster. Generally yes, but the optimal timing depends on your current resource reserves and your active biome's node HP profile.
Does the bulk bonus reset on rebirth?
No, the bulk bonus system and smelter upgrades persist across rebirths. Only your ore, level, and unsmelted inventory are wiped on a rebirth cycle. Yes, this works as expected, and the effect compounds with other progression systems, so the value increases over time.
Why the Bulk Bonus Numbers Shift Between Patches
The exact bonus percentages in the tables above shift slightly with each major patch, and the developers have publicly stated that the bulk bonus is a tuning knob they adjust to balance the smelter economy. If you notice the bonus dropping after a patch, do not panic — the underlying system is unchanged, and the bonus value typically returns to baseline within 1-2 patches.
The most reliable way to verify the current bonus value is to track your own smelter output over a 5-batch window and calculate the average bonus. Community-driven spreadsheets track these values across patches and provide a real-time view of the current bulk bonus.
How the Bulk Bonus Affects the Trade Economy
Because the bulk bonus gives an edge to players who smelt in large batches, the trade economy naturally favors players who can afford to queue 100-stack batches. A player with Smelter III and a full Mythril Bar queue can craft end-game drills faster than a player still on Smelter I, which translates into faster Drill Piece income and more aggressive trade offers.
For trade-focused players, the bulk bonus is not just a smelter optimization — it is a competitive advantage that compounds across the trade market. Investing in Smelter III is the single highest-leverage upgrade for players who want to dominate the trade economy.
The Hidden 75-Stack Bonus Tier
Most players focus on the 50-stack and 100-stack bonus tiers, but there is a hidden bonus tier at the 75-stack mark that is unlocked by the Smelter II upgrade. The 75-stack bonus sits between the 50-stack and 100-stack bonuses in value, and it is useful for players who cannot yet afford the Smelter III upgrade but want more bonus than the 50-stack offers.
| Tier | Bonus | Use Case |
|---|---|---|
| 50-stack | ~10-15% | Standard for every recipe |
| 75-stack | ~12-17% | Mid-game players with Smelter II |
| 100-stack | ~18-22% | End-game players with Smelter III |
The 75-stack tier is rarely discussed in the community because it sits in an awkward middle ground, but for players who are between Smelter II and Smelter III, it is a meaningful upgrade that improves smelter throughput by 5-10% over the 50-stack baseline.
How to Detect When the Bonus Is Disabled
Occasionally, the bulk bonus system can be temporarily disabled by a Roblox server lag spike or by a maintenance window. If you notice your smelter output dropping back to the base output (e.g., 10 Common Ingots from a 50/50 batch instead of 11-12), the bonus is likely disabled.
To recover, restart the Roblox client and re-queue the batch. The bonus typically returns within a few minutes of a client restart. If the issue persists, check the official Discord for any announcements about a known bulk bonus bug. Veteran players typically learn to recognize these patterns within the first 10-15 hours of focused play.