# Back-of-envelope math every telecom professional runs
A carrier exec sees a proposed handset subsidy deal, pulls out a phone calculator, and kills it in ninety seconds: "Payback is 34 months, our contract is 24. Pass." No spreadsheet, no model. Just five numbers she carries in her head. This lesson gives you those same five calculations.
Telecom deals move fast: spectrum auctions, MVNO (Mobile Virtual Network Operator, a company that sells mobile service over another carrier's network) wholesale terms, handset subsidies, fiber build business cases. Before anyone opens Excel, the room needs a gut check. These five calculations are that gut check.
ARPU (Average Revenue Per User, usually monthly) is the sector's central metric. As of 2025 estimates: US mobile ARPU runs roughly $40 to $48/month blended across carriers (Verizon, AT&T, T-Mobile all disclose this quarterly). European mobile ARPU is notably lower, often estimated at €12 to €18/month, reflecting more intense competition and regulatory pressure on roaming and pricing.
Churn rateChurn rateChurn rate is the percentage of customers or revenue lost over a period. It measures how fast a business loses its existing customer base.View full definition → is the percentage of customers who leave per period. Postpaid mobile churn in the US typically runs 0.7% to 1.2% monthly (estimate); European markets vary widely, sometimes higher due to easier number portability rules under EU telecom regulation.
Customer Lifetime Value (CLV), simplified:
CLV = ARPU / Monthly Churn RateThis works because 1/churn approximates average customer lifespan in months (a standard actuarial simplification for geometric retention).
Worked example: ARPU = $45/month, monthly churn = 1.5%.
CLV = 45 / 0.015 = $3,000That $3,000 is the ceiling for what you'd spend to acquire or retain that customer, before considering margin. Professionals often apply a gross margingross marginGross margin is the share of revenue left after subtracting the direct cost of producing goods or services, expressed as a percentage of revenue.View full definition → (telecom service margins commonly estimated at 55 to 65%) to get contribution-based CLVCLVLifetime Value: the total revenue (or profit) a customer generates throughout their entire relationship with your business.View full definition →: $3,000 × 0.60 ≈ $1,800.
Operators subsidize phones to win multi-year contracts. The question every finance person asks: how many months until the subsidy is recovered?
Payback (months) = Subsidy Cost / Monthly Margin ContributionWorked example: Carrier subsidizes a phone by $400 (device cost minus what the customer pays upfront). Monthly service margin contribution is $18.
Payback = 400 / 18 ≈ 22 monthsIf the contract term is 24 months, this deal barely works, and only if churn doesn't spike before month 22. This is exactly the calculation behind why carriers pushed customers toward installment plans (device payment plans separated from service) after roughly 2013 to 2015 in the US: it de-risks the subsidy math.
Network economics increasingly run on cost-per-GB delivered, used to judge whether pricing plans and infrastructure investment line up.
Cost per GB = Network Operating Cost (period) / Total Data Traffic (GB, same period)Estimates vary hugely by network type: mobile cost-per-GB is commonly cited in the range of a few cents to tens of cents depending on spectrum efficiency and site density; fixed fiber cost-per-GB is typically an order of magnitude lower because fiber capacity is cheap once the trench is dug. This is the core justification for fixed-mobile convergence strategies (bundling home broadband and mobile), pursued by BT/EE, Deutsche Telekom, and Comcast/Xfinity Mobile alike: push traffic onto the cheaper network.
Quick sanity check professionals use: if a carrier's cost-per-GB is rising while ARPU is flat, margins are compressing, a red flag in any pitch deck.
To eyeball a market size claim, multiply ARPU by subscriber count and compare to disclosed revenue.
US mobile market, rough 2025 estimate: approximately 340 to 350 million subscriber connections (including multi-device users), ARPU near $45.
350M × $45 × 12 months ≈ $189 billion annualizedThis is in the right ballpark of published US wireless service revenue estimates (commonly cited around $150 to $200 billion depending on what's included). If someone's pitch deck claims a $400 billion US mobile services market, the math doesn't hold, question it.
For Europe, fragmentation matters: no single "European carrier", instead national champions (Vodafone, Orange, Deutsche Telekom, Telefónica) plus the European Commission's regulatory push for a "Digital Single Market" that has repeatedly tried (with limited success) to encourage cross-border consolidation. Total EU mobile connections are estimated around 500 to 550 million (including multi-SIM), with lower per-user revenue than the US.
For anyone evaluating a spectrum auction or license transaction, the standard normalization is dollars per MHz-population (MHz-pop):
Price per MHz-pop = Total Price / (Spectrum Bandwidth in MHz × Population Covered)Worked example: A license covers 100 MHz across a population of 10 million, selling for $500 million.
$500M / (100 × 10M) = $0.50 per MHz-popThis lets you compare wildly different-sized deals apples-to-apples. US C-band auction (2021) prices were widely reported in the several-dollars-per-MHz-pop range for prime mid-band spectrum, an estimate that shows how much scarcer good mid-band spectrum was versus earlier auctions. For methodology and historical auction data, the FCC's own auction summaries are the authoritative free source.
Knowledge check
1. Why does dividing ARPU by monthly churn rate approximate Customer Lifetime Value (CLV)?
2. A telecom exec uses the basic CLV formula (ARPU / churn) to set a ceiling on acquisition spend, without adjusting for margin. What is the main risk of using this unadjusted number?
3. Why might a European telecom professional expect a lower CLV estimate than a US counterpart, all else equal, based on the sector context described?
4. Select ALL correct answers about why fast mental math calculations (like CLV) are valuable in telecom deal-making.
Select all the correct answers.
5. Select ALL correct answers about ARPU and churn as inputs to telecom decision-making.
Select all the correct answers.
None of these formulas require precision to the decimal. They require speed and skepticism. A few practical habits:
🎬 [VIDEO: "How Telecom Companies Make Money (ARPU, Churn, CLVCLVLifetime Value: the total revenue (or profit) a customer generates throughout their entire relationship with your business.View full definition → Explained)" - youtube.com - search for recent telecom analyst explainer videos covering these core unit economics; look for ones citing named carriers' quarterly filings]