📖 Overview
This calculator shows whether a renewal increase is manageable or dangerous.
It recomputes budget surplus and if needed estimates how long emergency savings can absorb the new monthly deficit.
🧪 Example Scenarios
Use these default and higher-pressure example inputs to explore how sensitive this calculator is before using your real numbers.
| Input | Base Case | Higher Pressure Case |
|---|---|---|
| Net Monthly Income ($) | 6,100 | 5,490 |
| Current Total Monthly Expenses ($) | 5,000 | 5,750 |
| Current Rent ($) | 2,100 | 2,415 |
| New Rent ($) | 2,550 | 2,933 |
| Emergency Savings ($) | 9,000 | 8,100 |
⚙️ How It Works
Measures post-renewal budget stress by recalculating monthly surplus/deficit after rent increase and estimating savings runway if cash flow turns negative.
The Formula
New Surplus = Income − (Current Expenses − Current Rent + New Rent)
| Income | Reliable net monthly take-home income |
| Current Expenses | Total monthly spend under current rent |
| Current Rent | Existing rent amount in current budget |
| New Rent | Proposed/renewal rent amount |
| Savings | Available emergency reserve to absorb deficits |
💡A small rent jump can flip a stable budget into persistent monthly deficit. Surplus sign change is often the most important threshold to monitor.
Quick Reference
| Monthly Deficit | Savings | Runway |
|---|---|---|
| $200/mo | $6,000 | 30 months |
| $350/mo | $6,000 | 17.1 months |
| $500/mo | $10,000 | 20 months |
When To Use This
- Use this tool when you need a fast decision during active planning or execution.
- Use this before committing money, time, or tradeoffs that are hard to reverse.
- Use this to compare options using the same assumptions across scenarios.
Edge Cases To Watch
- Results can be misleading if key inputs are missing, stale, or unrealistic.
- Very small or very large values may amplify rounding effects and interpretation risk.
- If assumptions change mid-decision, recalculate before acting.
Practical Tips
💡 Model both immediate and six-month adjusted spending plans.
💡 Separate negotiable vs fixed expenses before assuming cuts.
💡 Use runway output to define your renegotiation threshold.
Frequently Asked Questions
❓ If surplus stays positive, should I still worry?
Yes, but risk is lower. Track reduced savings velocity and new shock tolerance.
❓ Should emergency savings include investments?
Only include funds you can access quickly without major penalties.