In Python, load the data with pandas and compute net revenue retention from column totals for the whole period, or row by row for each month. On the sample data it returns 96.18.
NRR = (MRR at start + Expansion − Contraction − Churned) ÷ MRR at start × 100
What you need
Net revenue retention (NRR), or net dollar retention, is the share of recurring revenue you keep from existing customers after upgrades, downgrades and cancellations, as a percentage of what they paid at the start. You need these columns, here from the sample file monthly.csv:
- df["mrr_start"]: MRR at start of month
- df["mrr_expansion"]: expansion MRR
- df["mrr_contraction"]: contraction MRR
- df["mrr_churned"]: churned MRR
Step by step
- Install pandas (pip install pandas) and save monthly.csv next to your script.
- Run the script. The first print shows one row per month, the second the figure for the whole period.
- To use your own data, rename your columns to match, or change the names in the code.
The code
import pandas as pd
df = pd.read_csv("monthly.csv")
# Each month
df["nrr"] = (df["mrr_start"] + df["mrr_expansion"] - df["mrr_contraction"] - df["mrr_churned"]) / df["mrr_start"] * 100
print(df[["month", "nrr"]].round(2))
# Whole period: add up the parts first, then divide
nrr_total = (df["mrr_start"].sum() + df["mrr_expansion"].sum() - df["mrr_contraction"].sum() - df["mrr_churned"].sum()) / df["mrr_start"].sum() * 100
print(round(nrr_total, 2))
What you should get
Run against the sample data, the code above returns these values (in percent):
| Month | mrr_start | mrr_expansion | mrr_contraction | mrr_churned | nrr |
|---|---|---|---|---|---|
| 2026-01 | 1,80,000 | 6,000 | 3,500 | 9,000 | 96.39% |
| 2026-02 | 1,95,500 | 7,200 | 4,100 | 10,200 | 96.37% |
| 2026-03 | 2,12,900 | 6,800 | 3,900 | 11,800 | 95.82% |
| 2026-04 | 2,30,000 | 7,400 | 4,600 | 12,900 | 95.61% |
| 2026-05 | 2,41,400 | 8,100 | 4,200 | 12,100 | 96.60% |
| 2026-06 | 2,60,400 | 8,600 | 4,800 | 13,400 | 96.31% |
| Whole period | 13,20,200 | 44,100 | 25,100 | 69,400 | 96.18% |
(₹13,20,200 + ₹44,100 − ₹25,100 − ₹69,400) ÷ ₹13,20,200 × 100 = 96.18%
Notes for Python
- Dividing by zero in pandas does not raise an error: it gives inf or NaN. Check with df.replace([float("inf"), -float("inf")], float("nan")) before averaging or plotting.
- For the whole period, sum the columns first and then divide. df[col].mean() of the monthly results weights a small month the same as a large one.
- pct_change(), groupby() and resample() extend the same idea to weekly data, product categories and daily rows.
Where net revenue retention misleads
- Do not include new customers' revenue; NRR is about the customers you already had.
- A price rise lifts NRR once, without customers valuing the product more.
- Monthly NRR to the twelfth power approximates yearly NRR only if the rate is steady.
The full explanation, with a calculator, is on the Net revenue retention (NRR) page.
Same metric, other tools
Related metrics in Python (pandas)
Learn more about Python
- Python and SQL for data analysis, side by side — 3 min read
- How to find out what changed in your sales data — 2 min read
About the data on this page
The figures come from a small made-up dataset, printed above in full so you can check every number by hand. Download it as monthly.csv. The results are computed from those rows when the page is built, and the Excel formulas, SQL and Python on these pages are run against the same rows before publishing, so the code and the answers agree.
To get these numbers from your own data without writing formulas, try AnalyzeIt: ask in plain words and it shows the working behind every figure.
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