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STP calculator: move a lump sum into equity month by month.
Park an amount in a debt or liquid fund and move equal parts into equity each month. See the value after the holding period against a lump sum on day one and against leaving it all in debt.
- Formula shown
- Free, nothing stored
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- STP
- Lump sum
- Debt fund only
- Dynamic Asset Allocator, model
01How it works
In plain words.
A systematic transfer plan (STP) keeps a lump sum in a debt or liquid fund and moves a fixed part into an equity fund every month. Here the transfer, the amount divided by the months, happens at the start of each month. Money not yet moved earns the debt rate and money already moved earns the equity rate. The last transfer also moves the interest the debt fund earned, so nothing is left behind. The calculator runs this month by month and compares it with the whole amount in equity on day one and with all of it left in the debt fund.
The formula
id = (1 + debt return)^(1/12) - 1 and ie = (1 + equity return)^(1/12) - 1At the start of month k, for k < months: move T = amount / months (the last move takes the whole debt balance)Then every month: debt = debt x (1 + id), equity = equity x (1 + ie)Lump sum = amount x (1 + ie)^n; debt only = amount x (1 + id)^n; n = years x 1202Worked example
The default numbers, by hand.
Rs 10 lakh moved over 12 months, 7% a year in the debt fund, 12% a year in equity, held 10 years: each transfer is about Rs 83,300 and the debt fund earns about Rs 32,300 while the money waits. The STP ends near Rs 30.4 lakh, against about Rs 31.1 lakh for the lump sum on day one and about Rs 19.7 lakh left in the debt fund. At one constant equity return above the debt rate the lump sum always ends ahead; here spreading the entry costs about Rs 65,200.
| Input | Value |
|---|---|
| Amount to invest | ₹10,00,000 |
| Transfer over | 12 months |
| Debt or liquid fund return a year | 7% |
| Equity return a year | 12% |
| Holding period from the first transfer | 10 years |
| Result | Value |
|---|---|
| STP value after 10 years | ₹30.4 L |
| Lump sum into equity on day one | ₹31.1 L |
| Left in the debt fund | ₹19.7 L |
| Lump sum ahead of the STP by | ₹65,240 |
| STP ahead of staying in debt by | ₹10.7 L |
| Monthly transfer | ₹83,333 |
| Interest earned in the debt fund while waiting | ₹32,293 |
| The same STP at the Dynamic Asset Allocator model CAGR | ₹3.62 Cr |
03Key concepts
What to know before you use it.
Why an STP
An STP spreads the entry into equity over months, so a fall soon after the start hits only the part already moved. The money waiting earns a debt fund return instead of nothing, which narrows the gap to a lump sum compared with cash.
What a constant return cannot show
With one constant equity return above the debt rate, a lump sum always ends ahead, because more money is in equity for longer. An STP comes out ahead only when equity prices fall during the transfer months. Vanguard’s 2012 study found a lump sum ahead of spreading in about two thirds of rolling 10 year periods in the US, UK and Australia.
Good to know
- A 1 month STP is the same as a lump sum; a longer one keeps more money in debt for longer.
- Each transfer sells debt fund units, which can create a taxable gain on the interest earned; this calculator does not deduct tax.
- The lump sum vs SIP calculator shows the same idea with the waiting money earning nothing.
04Assumptions
What the calculator assumes.
- One constant return for the debt fund and one for equity; transfers at the start of each month.
- Money not yet transferred earns the debt rate; the last transfer also moves the interest earned.
- Tax, exit load and expense ratio are not deducted; the capital gains tax calculator covers the tax on equity gains. The defaults of 7% for debt and 12% for equity are assumptions for illustration, not forecasts.
Sources, checked 12 Oct 2026
05Questions
Asked about the STP calculator.
What is an STP in mutual funds?
A systematic transfer plan moves a fixed amount from one fund to another at a fixed interval, usually from a liquid or debt fund into an equity fund of the same fund house. It is a way to invest a lump sum in parts.
Is STP better than lump sum?
At one constant equity return above the debt rate, the lump sum ends ahead because it is in equity for longer. An STP ends ahead when equity prices fall during the transfer months. The calculator shows the gap at the returns you enter.
What is the difference between STP and SIP?
A SIP invests new money from your bank account every month. An STP invests money you already have, parked in a debt fund, in monthly parts.
How long should an STP run?
There is no single answer; it is a trade off between spreading the entry and time in equity. Try 6, 12 and 24 months in the calculator and compare the gap with the lump sum.
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06Keep going
Learn the idea, see it applied.
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Education only, not investment advice. RupeeCase (QC Alpha Technologies Pvt Ltd) is not a fund, a PMS or a SEBI registered investment adviser. Model returns are back tested, not a promise; figures carry the date checked.