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Convertible Note Calculator: Interest, Valuation Cap & Conversion

See what a convertible note turns into. The calculator adds simple interest up to conversion, compares the cap price with the discounted round price, and shows the shares issued, ownership and founder dilution in the next priced round.

QUICK ANSWERA convertible note converts principal plus accrued interest into shares at the next round, at the lower of the cap price (cap ÷ pre-round shares) and the round price minus the discount. Example: ₹2.5 Cr at 8% for 18 months accrues ₹30 L, so ₹2.8 Cr converts.

Converting amount = Principal × (1 + rate × years)
Cap price = Cap ÷ Shares before conversion
Discount price = Round price × (1 − discount)
Shares = Converting amount ÷ lower price

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⚠️ Educational model; your signed note governs conversion. Not legal or tax advice.

What the Convertible Note Calculator does

✅ Simple interest to conversion date
✅ Cap vs discount comparison
✅ Option to pay interest in cash
✅ Shares and ownership after the round
✅ Founder dilution summary

How to use the Convertible Note Calculator

STEP 1
Enter your numbers
Type the figures you know. Every field starts with a realistic example so you can see how it works.
STEP 2
Read the result instantly
Results, tables and the plain-English explanation update as you type. No submit button, no login.
STEP 3
Test scenarios
Change one assumption at a time (valuation, growth, dilution, exit) to see what really moves the outcome.
STEP 4
Share or save
Copy the summary, send it on WhatsApp or print to PDF for your co-founders, board or investment committee.

Convertible notes in Indian startups

A convertible note is debt that converts into equity at a future round. Under FEMA and the Companies Act, only DPIIT-recognised startups can issue convertible notes, each investor must put in at least ₹25 lakh in a single tranche, and the note must convert or be repaid within 10 years.

Interest on notes is usually simple, often 0–10% a year, and normally converts along with the principal. Because interest increases the converting amount, a note held for a long time dilutes founders more than a SAFE with the same cap.

Worked example

₹2.5 Cr note, 8% simple interest, 18 months, ₹25 Cr cap, 20% discount; next round ₹12 Cr at ₹50 Cr pre-money on 10 lakh shares. ₹2.8 Cr converts at the cap price of ₹250 per share (the discounted round price is higher), giving about 11,200 shares.

Frequently asked questions

How is interest on a convertible note calculated?

Usually simple interest: principal × annual rate × time. ₹1 Cr at 8% for 2 years accrues ₹16 L, so ₹1.16 Cr converts.

What happens if there is no priced round before maturity?

It depends on the note: it may convert at a pre-agreed valuation, be extended, or become repayable. Indian notes must convert or be repaid within 10 years.

Convertible note or SAFE, which is better for founders?

SAFEs carry no interest or maturity, so they are simpler and slightly less dilutive. In India, notes have clear legal backing for DPIIT startups while US SAFEs do not; many Indian seed rounds use iSAFEs or CCPS instead.

Is this tool free? Do I need to sign up?

Yes. It is completely free, needs no login and has no usage limit. FastFee builds payment collection software; these startup and investor tools are free resources for founders, angels and fund managers.

Is my data private?

Yes. Everything you type stays in your own browser on this device (local storage). Nothing is uploaded to FastFee. Export or print a copy if you need to keep it.

Use it together with

SAFE Calculator →Model one or more SAFEs converting in a priced round: cap vs discount, shares and dilution.Pre-money & Post-money Calculator →Post-money, investor %, founder % and price per share in one step, including ESOP pool shuffle.

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