Purchase Impact Calculator
How much does that big purchase really cost in FIRE years?
The “true cost” is $30,000 — what $30,000 would have grown to over the No delay delay at 4.4% real return.
How This Works
We compute your years-to-FIRE twice: once with your current savings, and once with savings minus the purchase amount. The difference is your FIRE delay.
The “true cost” compounds the purchase amount at your real return rate over the delay period: True Cost = Purchase × (1 + Real Return)^Delay. This represents the total portfolio value you forgo.
All calculations run entirely in your browser. We don't store or transmit any of your financial data.
Frequently Asked Questions
What is the 'true cost' of a purchase?
The true cost accounts for the compound growth you miss by spending money instead of investing it. A $30,000 car at 5% real return doesn't just cost $30,000 — it costs the $30,000 plus all the growth that money would have generated until you reached FIRE.
Should I never make big purchases?
No — this tool helps you make informed decisions, not avoid spending. A purchase that delays FIRE by 2 months might be well worth it. A purchase that delays it by 3 years deserves careful thought.
Does this work for recurring expenses?
This calculator models one-time purchases that reduce your savings. For recurring expenses (like a car payment), adjust your annual expenses in the FIRE Number Calculator instead.
What if my purchase also saves me money?
If a purchase reduces your annual expenses (e.g., solar panels, an efficient car), reduce your Annual Expenses slider to reflect the savings. The calculator will show the net effect.