---
title: "Subscription interval: definition and formula"
description: "How often a subscription ships: every 30 days, every 60. It sets how many renewals fit in a year, and so how fast a subscriber pays back."
url: https://offersuite.io/glossary/subscription-interval
updated: 2026-10-13
---

# Subscription interval

How often a subscription ships: every 30 days, every 60. It sets how many renewals fit in a year, and so how fast a subscriber pays back.

## In plain words

A subscription interval is the time between deliveries. It is chosen to match how fast the product is used up: monthly for a bag of coffee, every two or three months for something that lasts longer.

The interval sets the clock for everything else. A subscriber on a 60-day interval takes half as many renewals in a year as one on 30 days. Each renewal may keep the same margin, but the value arrives half as fast, and the acquisition cost takes twice as long to come back.

## Formula

- Renewals due within a horizon = horizon in days ÷ interval in days, rounded down
- Month a renewal lands in = renewal number × interval ÷ days in a month

## Worked example

Shipped every 30 days, a coffee subscriber is expected to take 4.24 renewals in twelve months, is worth $53.29 over the year and pays back in month 5.

Shipped every 60 days, on the same renewal rates per order, the engine expects 2.85 renewals. The subscriber is worth $37.11 over the year and pays back in month 10.

### The example order

A $40.00 bag of coffee, shipped free, every cost counted

Revenue $40.00 to contribution margin $15.36 (38.4%)

Revenue

$40.00

Cost of goods

−$12.00

Pick and pack

−$1.18

Packaging

−$0.50

Shipping label

−$7.50

Card fee per order

−$0.30

Refunds

−$2.00

Card processing

−$1.16

Contribution margin

$15.36

2 declared kinds cost nothing on this option

Computed by the margin engine in Offer Suite's own code, in whole cents, from a $40.00 bag of coffee with a $12.00 unit cost.

## A longer interval is not simply half the value

Subscribers on an interval that matches their use tend to stay longer, because product does not pile up. A shorter interval than the customer needs brings more orders at first and more cancellations soon after. The right interval is the one the customer's cupboard agrees with.

## Using it

Offer the interval that matches real use, and let subscribers change it. A subscriber who can move to every six weeks is one who did not cancel. When you compare offers with different intervals, compare them over the same number of months. Counting renewals favours whichever ships more often.

## Related

- [Glossary **Glossary of offer economics** The terms behind offer profit, defined plainly with their formulas and a worked number: contribution margin, profit per visitor, break-even lift and more.](https://offersuite.io/glossary)
- [Calculator **Subscription payback calculator: CAC and churn** How much a subscriber's first order loses against what you paid to acquire them, how many renewals it takes to earn that back with churn, and in which month.](https://offersuite.io/calculators/subscription-payback)
- [Calculator **Subscription intro offer calculator** Subscribe and save, a discount on the first order, a free trial or a free product: each as a cohort of subscribers with the same costs, ranked on profit per visitor after acquisition.](https://offersuite.io/calculators/subscription-intro-offer)
- [Glossary **Renewal order: definition, formula and example** A subscription order the subscriber didn't place by hand, billed by the subscription contract. Priced at the renewal price, without first-order-only costs.](https://offersuite.io/glossary/renewal-order)
- [Glossary **CAC payback period: definition, formula and example** How long a customer takes to earn back what they cost to acquire. With churn counted, it is later than the simple division suggests.](https://offersuite.io/glossary/cac-payback-period)
- [Glossary **Customer lifetime value (LTV): definition** The profit a customer brings over the orders they stay for: the first order's margin plus each later order's, weighted by who is still buying.](https://offersuite.io/glossary/customer-lifetime-value)