Analyse simple and compound present/future values alongside net present value (NPV) and internal rate of return (IRR). Save scenarios with the shareable URL or keep them handy via the favourites button.
Inputs
How it’s calculated
- Simple interest: FV = PV·(1+r·t); present value reverses the relation.
- Compound interest: FV = PV·(1+r/m)^(m·t); continuous: FV = PV·e^(r·t).
- NPV = Σ CFk/(1+r)tk at discount rate r; multiple scenarios compare different r values.
- IRR is the rate where NPV = 0; the solver uses bracketed numeric search with convergence checks. Some cash‑flows can yield multiple roots.
- The shareable URL stores inputs and the cash‑flow table so anyone can reproduce your scenario.
Results
Results are provided for educational use only. Taxes, fees, and product-specific conditions are not considered—please verify decisions with a qualified adviser.
How to use this calculator effectively
This guide helps you use Simple & Compound Interest, NPV & IRR Calculator in a repeatable way: define a baseline, change one variable at a time, and interpret outputs with explicit assumptions before you share or act on results.
How it works
The page applies deterministic logic to your inputs and shows rounded output for readability. Treat it as a comparison workflow: run one baseline case, adjust a single parameter, and measure both absolute and percentage deltas. If a result seems off, verify units, time basis, and sign conventions before drawing conclusions. This approach keeps your analysis reproducible across teammates and sessions.
When to use
Use this page when you need a fast estimate, a classroom check, or a practical what-if comparison. It works best for planning and prioritization steps where you need direction and magnitude quickly before investing in deeper modeling, manual spreadsheets, or formal external review.
Common mistakes to avoid
- Changing multiple parameters at once, which hides the true cause of output movement.
- Mixing units (percent vs decimal, monthly vs yearly, gross vs net) across scenarios.
- Comparing with another tool without aligning defaults, constants, and rounding rules.
- Using rounded display values as exact downstream inputs without re-checking precision.
Interpretation and worked example
Run a baseline scenario and keep that result visible. Next, modify one assumption to reflect your realistic alternative and compare direction plus size of change. If the direction matches your domain expectation and the size is plausible, your setup is usually coherent. If not, check hidden defaults, boundary conditions, and interpretation notes before deciding which scenario to adopt.
See also
FAQ
What is the difference between simple and compound interest?
Simple interest applies the rate to the original principal only. Compound interest reinvests each period's interest so the balance accelerates over time. Reviewing both side by side helps you gauge the opportunity cost of not compounding.
Why can't the IRR be calculated?
IRR requires at least one negative and one positive cash flow. Some patterns produce multiple IRRs or none at all, so the solver may fail to converge. Adjust the cash flows or rely on the NPV table to compare scenarios.
What should I do first on this page?
Start with the minimum required inputs or the first action shown near the primary button. Keep optional settings at defaults for a baseline run, then change one setting at a time so you can explain what caused each output change.
Why does this page differ from another tool?
Different pages often use different defaults, units, rounding rules, or assumptions. Align those settings before comparing outputs. If differences remain, compare each intermediate step rather than only the final number.
How reliable are the displayed values?
Values are computed in the browser and rounded for display. They are good for planning and educational checks, but for regulated or high-stakes decisions you should validate assumptions with official guidance or professional review.
Related calculators
How it's calculated
- Supports simple, compound, and continuous compounding.
- NPV uses discounted cash flows; IRR solved numerically (bracketing).
- Cash‑flow sign convention is indicated; units shown clearly.
- Share URL keeps scenario parameters.