Lumpsum + SIP Calculator
Combine a one-off lump-sum and a monthly SIP at a fixed return to show the merged future value and each part's contribution.
Input Data
Results
At a glance:The Lumpsum + SIP calculator computes the merged FV of 'invest a lump up front, then add a monthly SIP', splitting the lump part and the SIP part. Monthly compounding: i = annual ÷ 12, n = years × 12; lump FV = P × (1+i)^n; SIP FV = monthly × [((1+i)^n − 1) ÷ i] × (1+i) (begin-annuity); merged = sum. This hybrid combines the lump's early full compounding with the SIP's steady, timing-diversified accumulation — close to most people's real situation (a savings pot + monthly salary surplus).
Formula
i = annual ÷ 12; n = years × 12.
Lump FV = P × (1+i)^n; SIP FV = monthly × [((1+i)^n − 1) ÷ i] × (1+i).
Merged FV = lump + SIP; total invested = lump + monthly × n; gain = FV − invested.
$$FV_{lump} = P (1 + i)^{n}$$$$FV_{sip} = A \cdot \dfrac{(1+i)^{n}-1}{i} (1+i), \quad i=\dfrac{r}{12},\; n=12t$$How to Use
- Enter the one-off lump principal.
- Enter the monthly SIP, expected annual return and years.
- View the merged FV and each part's contribution and gain.
100k lump + 5k/month at 12% for 10 years — merged FV breakdown
| Item | Amount | Note |
|---|---|---|
| Lump part FV | HK$330,039 | 100,000 × (1.01)^120 |
| SIP part FV | HK$1,161,695 | 5,000 × begin-annuity factor |
| Merged FV | HK$1,491,734 | Sum of both |
| Total invested | HK$700,000 | 100,000 + 5,000 × 120 |
| Gain | HK$791,734 | Merged − invested |
SIP FV (~1.16m) far exceeds lump FV (~330k) because of the invested amount: SIP puts in 600k over 10 years (6× the lump). The lump compounds longer but is smaller; the SIP is larger but averages a shorter compounding period.
Case Studies
Case 1: A lump up front plus steady monthly for 10 years
May invests HK$100,000 lump-sum, then HK$5,000/month at 12% (monthly) for 10 years.
Lump FV = 100,000 × 1.01^120 ≈ 330,039; SIP FV = 5,000 × ((1.01^120 − 1)/0.01) × 1.01 ≈ 1,161,695; merged ≈ 1,491,734. Invested = 100,000 + 5,000×120 = 700,000; gain ≈ 791,734.
Reading: 700k in, ~1.49m out after 10 years, gain 791k exceeds principal — the result of 'idle cash in early + cash flow added + long compounding'.
Case 2: Why the SIP part exceeds the lump part
Many wonder: the lump's 100k 'compounds early and in full', yet its FV (~330k) is far below the SIP part (~1.16m).
The key is total principal: the lump only puts in 100k; the SIP puts in 5,000×120 = 600k over 10 years, 6× the lump. Though each SIP instalment compounds shorter, the far larger amount wins. FV is driven by 'how much' and 'how long'.
Notes: (1) raise the lump to match the SIP total and the lump part overtakes (same money, lump compounds longer); (2) FV is rate-sensitive and subject to sequence risk; (3) nominal FV ignores inflation/tax/fees; (4) model assumes fixed SIP — if you raise it yearly, reality is higher. For pure strategies use the lumpsum and SIP calculators.
FAQ
Why 'lump + SIP'; what is the benefit?
It combines two mainstream strategies to take both advantages. Lump-sum invests idle cash in full at the start — earliest, fullest compounding, theoretically largest in a rising market; downside is timing risk (buy at a high). SIP uses cash flow monthly — dollar-cost averaging diversifies timing risk and builds discipline, no big sum needed up front; downside is later money compounds less. Combining: put 'existing savings' in lump (compound early) and 'monthly surplus' in SIP (add via cash flow, diversify). This fits most people — a pot plus monthly salary surplus. The calculator splits the two parts so you see each contribution and plan the best 'first lump vs monthly' mix.
Why is the SIP part's FV so much larger?
Because of the total principal. Default: lump 100k, SIP 600k over 10 years (6×). Although each SIP instalment compounds shorter, the much larger amount yields a higher FV. FV is driven by 'amount' and 'time'. Raise the lump to the SIP total and the lump overtakes (same money, lump compounds longer). That is why splitting the parts helps you tune the ratio.
What to watch; is the result guaranteed?
This uses a fixed return and steady monthly compounding — clear on mechanics, but: (1) FV is not guaranteed, returns fluctuate and may lose; SIP is sequence-risk sensitive (same average, different order → different result), not reflected here; (2) rate assumption is extreme — use conservative; (3) no inflation — use real return for purchasing power; (4) no tax/fees — funds' expense ratios lower net return; (5) SIP fixed, no yearly step-up; (6) rounded. For understanding/planning, not a return promise. Consult a licensed professional.
How to split first lump vs monthly SIP?
No universal best ratio — depends on idle cash, cash flow, risk tolerance and market view. Framework: (1) how much idle cash vs stable monthly investable surplus — the lump comes from 'saved, not needed soon', the SIP from 'salary surplus'; (2) timing risk vs psyche — more lump = more concentrated timing risk; more SIP = stronger averaging, calmer; (3) market valuation — high valuation, less lump/more SIP; reasonable/low, more lump; (4) a common steady approach: invest part of idle cash as lump (not all), keep the rest as SIP/ammo. Try combinations here (fix total, vary the split) and decide with your cash flow and risk. Success hinges more on 'persist, diversify, low cost, don't panic' than on the optimal ratio. Pair with the lumpsum and SIP calculators.
What real factors lower the result?
Several: (1) returns fluctuate, not guaranteed; SIP sequence risk not reflected; (2) inflation erodes purchasing power — use real return (nominal minus inflation), pair with the real-rate-of-return calculator; (3) tax and fees (expense ratios, loads) compound away return over time; (4) SIP not stepped up — if you raise it yearly, reality is higher (use a growing-annuity calculator); (5) mid-way withdrawal/stops lower the result; (6) rounding. Use as a magnitude/planning reference with conservative, net-of-inflation-and-fee returns, and keep an emergency fund. Pair with the real-rate-of-return, investment-fee and growing-annuity calculators.
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References
Content review: Calculatorism Finance Team. Results are for reference only; please refer to the relevant authorities for the official figures.