Guesstimate Data Cheatsheet
The macro + micro anchors to size almost anything — memorise the spine, round hard, always sanity-check.
Every guesstimate is a chain of multiplications hanging off one or two anchor numbers — India's population, its households, its GDP. Get the anchor right and round everything else; an interviewer forgives ₹-rounding, never a 10× anchor error. This is the spine: macro on top, the segments and per-capita rates below. Memorise the bold ones.
TL;DR · Key Takeaways
Memorise this spine
- People ~1.46 bn · Households ~300 mn · Workforce ~990 mn — almost everything funnels from one of these.
- ~1/3 urban, 2/3 rural; median age 29 — never assume an urban, middle-class default.
- GDP ~$4.1 tn (~₹340 lakh cr) · per-capita ~₹19k/month — the size and spend anchors.
- Digital: ~900 mn online, ~700 mn UPI txns/day; Mobility: ~300 mn two-wheelers vs ~55 mn cars.
- Round to powers of ten, segment with the income pyramid, and always cross-check against a second anchor.
The anchor numbers
Who they are: people structure
What they earn: the income pyramid
The economy + digital + mobility
Going deeper → use the Industry Primers
The digital, mobility and sector figures above are quick national anchors for fast sizing — not sector depth. When a guesstimate is really about one industry, open its Industry Primer for ARPU, GMV, penetration, capacity and sales-mix numbers instead of reinventing them here: Telecom, Payments, E-Commerce, Food Delivery, Automobile, Electric Vehicles, FMCG, Retail, Banking, Healthcare, Power, Oil & Gas — plus ~15 more under Industry Primers in the sidebar.
Conversions & time constants
| Quantity | Value | Handy form |
|---|---|---|
| 1 lakh | 100,000 = 10⁵ | 0.1 million |
| 1 crore | 10,000,000 = 10⁷ | 10 million = 100 lakh |
| 100 crore | 1,000,000,000 | 1 billion |
| ₹1 lakh crore | ₹1 trillion | ≈ $12 billion |
| Minutes / day | 1,440 | ≈ 1,000 waking minutes |
| Hours / year | 8,760 | ≈ 8,000 (round) |
| Working days / yr | ~250 (5-day) · ~300 (6-day) | retail/footfall: ~300–360 |
| Weeks / year | 52 | ~4.3 weeks/month |
Per-capita consumption rates
| Item | Rate (planning anchor) | Use it for |
|---|---|---|
| Electricity | ~1,300 kWh / person / yr | power demand, grid sizing |
| Water (urban domestic) | ~135–150 L / person / day | tankers, supply, RO demand |
| Municipal solid waste (urban) | ~0.45 kg / person / day | garbage trucks, landfills |
| Petrol+diesel | ~100 kg fuel / person / yr (national avg) | fuel demand, petrol pumps |
| Cereal/food grain | ~180 kg / person / yr | FMCG staples, PDS |
| Milk | ~440 g / person / day | dairy, cold chain |
| Mobile data | ~25–30 GB / user / month | telecom, towers |
Default planning assumptions
| Assumption | Default | Why / nuance |
|---|---|---|
| Avg household size | ~4.8 (urban ~4.2, rural ~5.2) | people ÷ this = households |
| Adults (15+) share | ~70% of population | earners, voters, phone owners |
| Literacy rate | ~78% | any text/app-dependent product |
| Smartphone penetration | ~55–65% of people | rising fast; urban much higher |
| Replacement cycle — phone | ~3 years | stock ÷ cycle = annual sales |
| Replacement cycle — car | ~10–12 years | stock-and-flow sizing |
| Replacement cycle — TV/fridge | ~8–10 years | consumer durables |
| Metro size (tier-1) | Delhi-NCR ~32 mn · Mumbai ~21 mn · Kolkata/Bengaluru ~13 mn | city-level builds |
| Eating-out frequency (urban) | ~4–6 paid meals / week | QSR, delivery, restaurants |
How to use this in 30 seconds
1) Pick the anchor closest to your question (people, households, workforce, GDP). 2) Funnel with one ratio at a time from the pyramid/rates above, saying each assumption aloud. 3) Round hard — work in crores and powers of ten. 4) Sanity-check the answer against a different anchor (e.g., a per-capita-spend cross-check on a population-built number). If the two agree within ~2×, you're safe.
Read the data honestly (adversarial note)
These are mid-2026 planning anchors, deliberately rounded — cite them as "≈". Three to keep straight: (a) household count varies by source (~250 mn registered vs ~300 mn implied at size 4.8) — state which you use; (b) smartphone figures range widely (~750 mn primary users vs >1 bn devices) — pick a lane; (c) sector GDP share (agri ~18%) ≠ employment share (agri ~45%). For anything high-stakes, re-verify against the primary source (MoSPI, RBI, NPCI, IMF) — India's 2027 census will reset several of these.