Cut A Rock

Guide

Cut a Rock Tools

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We provide two interactive calculators for Cut a Rock, each built to solve a concrete progression decision before you spend Robux or commit mining time. The Robux budget planner takes your wallet balance, your progression stage, and the items you already own to construct a priority purchase list that avoids duplicate purchases. The Nova Prism odds calculator uses the room ceiling drop percentages to compute your probability of finding at least one Nova Prism stone across a target number of mined rocks. Both calculators run calculations locally in your browser using verified store prices and room drop tables captured from official platform data.

Tool 1: Robux budget planner

The Robux budget planner helps you spend your Robux efficiently by preventing wasteful spending on standalone boosts if you qualify for a bundle, and blocking purchases of bundles if you already bought individual components.

  • What you input: Your total Robux budget, your current game stage, and checkboxes for items you currently own (including 2x Money, 2x Machine Speed, 2x AFK Speed, 2x Power, and the four anvil passes).
  • What it outputs: A sequential, deduplicated purchase list matching your budget, showing exactly which items to buy and how much Robux remains.
  • Pricing data source: The official Roblox developer product and game pass endpoints captured on 6 November 2026, including 79 Robux for individual 2x boosts, 249 Robux for the Ultimate Boost Bundle (Permanent), and 199, 299, 399, and 499 Robux for anvil passes.
  • Practical example: If you enter a budget of 300 Robux at stage 1 with zero items owned, the tool recommends buying the Ultimate Boost Bundle (Permanent) for 249 Robux, leaving 51 Robux in reserve. This single recommendation prevents you from mistakenly spending 316 Robux by purchasing the four 79-Robux boosts individually.

To build your personalized spending plan, open the Robux budget planner.

Tool 2: Nova Prism odds calculator

The Nova Prism odds calculator models the binomial drop chance of finding the rare Nova Prism stone during a mining run.

  • What you input: Your selected room (Room 2 or Room 3) and the number of rocks you plan to mine.
  • What it outputs: The cumulative probability of finding at least one Nova Prism stone, the chance of finding zero stones, and the number of rocks required to hit a 50 percent probability benchmark.
  • Drop rate data source: The rock rarity percentages recorded directly from the room ceiling drop boards in the guide video:
    • Room 2: Common 50%, Uncommon 50%, Nova Prism 0.1%.
    • Room 3: Common 35%, Uncommon 50%, Rare 15%, Nova Prism 0.1%. (Percentages on the Room 1 ceiling board could not be cleanly read from the video frames, so calculations are available for Room 2 and Room 3).
  • Practical example: With Nova Prism set at 0.1% (a 1 in 1000 chance per rock), mining 100 rocks yields a 9.52% chance of finding at least one Nova Prism. Mining 500 rocks increases your chance to 39.36%, and reaching a 50% likelihood requires mining 693 rocks.

To test your planned mining runs against published drop tables, open the Nova Prism odds calculator.