What is Net Dollar Retention?
Net Dollar Retention (NDR) is functionally identical to Net Revenue Retention (NRR). Both measure how much revenue you retain and grow from existing customers. The terms are used interchangeably across the industry.
NDR above 100% means your existing customer base is growing without new acquisitions. This is the hallmark of a sticky product with strong expansion mechanics.
Why NDR Matters
NDR is arguably the best single metric for product-market fit in SaaS. If customers stay and spend more, your product is delivering value. If they leave or spend less, something is broken.
Public SaaS companies report NDR as a key metric. Best-in-class companies like Snowflake, Datadog, and Twilio have reported NDR above 130%, indicating exceptional customer value expansion.
How to Calculate NDR Step by Step
Step 1: Pick a customer cohort and time period. NDR is typically calculated annually on a specific cohort. Choose customers acquired in a specific year or quarter.
- Cohort: All customers active on Jan 1, 2025
- Their combined ARR on Jan 1, 2025: $1,200,000
Step 2: Look at the same cohort one year later. On Jan 1, 2026, what's their combined ARR? Only track these specific customers. Exclude anyone acquired after Jan 1, 2025.
- Some expanded (upgrades, seats): +$180,000
- Some contracted (downgrades): -$48,000
- Some churned (cancelled): -$72,000
- Ending ARR from this cohort: $1,260,000
Step 3: Divide ending by starting ARR.
- NDR = $1,260,000 ÷ $1,200,000 = 105%
Your 2025 cohort grew 5% without any new sales. Healthy, but room for more expansion.
Step 4: Calculate NDR for each cohort vintage. Your 2024 cohort and 2025 cohort may behave very differently:
- 2023 cohort NDR: 112% (mature, expanding steadily)
- 2024 cohort NDR: 105% (still ramping)
- 2025 cohort NDR: 98% (too early, some initial churn)
This reveals whether retention improves as customers mature.
Step 5: Pair NDR with GRR. NDR of 105% sounds good, but if GRR is only 82%, you're losing 18% of revenue and relying on expansion to mask it. See GRR for the full picture.
Common mistakes founders make:
- Calculating NDR the same way as NRR but calling it different (they are effectively the same metric; just be consistent)
- Using monthly data and not annualizing properly
- Including new customers in the cohort
- Reporting NDR without also reporting GRR (investors want both)
NDR Benchmarks
Below 90%: Concerning. You have a retention problem. 90-100%: Stable but not expanding. 100-120%: Good. Healthy expansion. Above 120%: Excellent. Strong product-market fit.
Formula
NDR = (Starting ARR + Expansion - Contraction - Churn) ÷ Starting ARR × 100
Same as NRR but often calculated annually on cohorts
Example
Cohort analysis for customers acquired in 2024:
- Starting ARR (Jan 2024): $1,000,000
- Ending ARR (Jan 2025): $1,150,000
- Expansion: $250,000
- Contraction: $50,000
- Churn: $50,000
NDR = $1,150,000 ÷ $1,000,000 = 115%
This cohort grew 15% without any new sales. Excellent retention and expansion.