About Poptani Labs

POPTANI

LABS

IDEAS WORTH BUILDING.

Poptani Labs is a small workshop for free web tools. It started with a Systematic Withdrawal Plan (SWP) simulator for Indian mutual funds and has grown into a wider collection — all free, no sign-up, everything running in your browser.

What lives here

• SWP Simulator — replay a withdrawal plan on real daily NAV history: pick a scheme, a lumpsum and a monthly withdrawal, and see exactly how the corpus would have evolved, withdrawal by withdrawal, with the remaining value and XIRR of the full cashflow.
• SIP Calculator — what a monthly SIP would actually have grown to, replayed on real NAVs across 1, 3, 5 and 10 years.
• Fund X-Ray — check stock overlap between two to four funds, so you can see hidden concentration before you buy a fifth fund that owns the same stocks.
• EMI Calculator — loan EMI with full prepayment modeling: part-payments, their timing, and what each one saves in interest and tenure.
• PDF utilities — a dozen everyday PDF tools that run entirely in your browser; your files never leave your device.
• Your Day in the Cosmos — the NASA Astronomy Picture of the Day for any special date: birthdays, anniversaries, weddings.
• Ink Guess — a draw-and-guess game: six quick rounds against the clock while our own sketch AI, trained on 132,000 hand drawings, guesses live in your browser. The playful corner of the lab.

Where the data comes from

Scheme lists and NAV histories come from mfapi.in, a free community API for Indian mutual fund NAVs. The scheme list refreshes daily; each scheme's full NAV history is fetched on demand when you select it.

How the math works

• Your lumpsum buys units at the NAV prevailing on (or nearest before) your investment date.
• Each scheduled withdrawal redeems units at that date's NAV. If a withdrawal exceeds the balance, the plan pays out the remainder and ends.
• Remaining value is marked at the latest available NAV; XIRR is computed over the full cashflow (lumpsum out, withdrawals in) with Newton's method.

Who is behind it

Built by Pawan Poptani as an open learning project — first as a Python/Streamlit app, now as a fast static website. The original code lives on GitHub.