Sell Lemons ROI Calculator

How to Use This Calculator

Add each upgrade you are considering with its Cost, your Income Before buying it, and your expected Income After buying it. Add multiple upgrades to compare them side by side. The calculator ranks them by ROI time and priority score so you know exactly which upgrade to buy first for maximum efficiency.

What Each Input Means

Formula and Estimate Logic

ROI Time = Upgrade Cost ÷ (Income After − Income Before). The upgrade with the shortest ROI time pays for itself fastest and should be bought first. Priority Score also factors in cost efficiency and stage weighting. Upgrades that unlock new systems may score higher than pure ROI suggests.

When to Use This Tool

Use this calculator whenever you have enough cash to buy an upgrade and are unsure which one to prioritize. It is especially useful in early-to-mid game when there are multiple competing upgrades. After each purchase, recalculate with updated income values since the best upgrade changes as your situation changes.

Common Mistakes

• Always buying the cheapest upgrade — it may not have the best ROI
• Not recalculating after each purchase — rankings change as income changes
• Using base income instead of post-multiplier income for the "Before" and "After" fields
• Ignoring upgrades that unlock new systems — their value goes beyond pure ROI

FAQ