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Windmill is priced by the number of active members (seats) a company has on the platform.
Our goal is to make it effortless to pilot Windmill while ensuring costs scale predictably as adoption grows.

Seats & Pricing

SeatsPrice
Free tier seatsFree
Each additional seat$10 USD per seat / month
Every Windmill plan includes a set of free seats. The exact number depends on your plan.

Why include free seats?

This lets HR teams, pilot groups, or early champions explore Windmill risk-free before rolling it out company-wide.

How Billing Works

Monthly subscription

  • We bill your default payment method once per month, at the beginning of the billing period (via Stripe).
  • The invoice total is based on the seat count at the start of the billing period.
  • Seats added mid-cycle are invoiced immediately, prorated for the remaining days.

Metered seat counting

  • A seat is any active member account during the month.
  • Inviting an employee to Windmill counts as a member, even if they haven’t logged in yet.
  • Deactivated or deleted users no longer count toward your total.

Automatic sync

  • Windmill regularly updates Stripe with your active seat count.
  • If your usage changes, we adjust your subscription item quantity accordingly.

Proration Rules

Windmill follows industry-standard proration logic:
ScenarioWhat happensWhy
Seat count increases mid-cycleWe immediately add the extra seats and prorate the charge for the remaining days in the cycle.You gain access right away and only pay for what you use.
Seat count decreases mid-cycleWe reduce the seat count for the next billing cycle (no mid-cycle refund).Prevents invoice churn and keeps billing predictable.

Example Invoices

The example below assumes a plan that includes 25 free seats. Substitute your own free tier number to estimate your invoices.
DateEventSeats ActiveCharge
Jan 1Billing cycle starts25$0 (within free tier)
Jan 10Add 5 users30Prorated charge for 5 seats × 22 days
Feb 1Invoice305 paid seats × $10 = $50
Feb 15Remove 8 users22No refund; reduced count applies to Mar invoice
Mar 1Invoice22Back to $0

Frequently Asked Questions

Do I ever lose my free seats?

No. Your plan’s free tier seats are always free, no matter how many total seats you have.

What counts as an “active” seat?

Any user that can log in and use Windmill during the billing period.

How do I estimate my bill?

  1. Count employees expected to be active.
  2. Subtract the free seats included in your plan.
  3. Multiply the remainder by $10.
Example (assuming a plan with 25 free seats):
90 users → (90 − 25) × $10 = $650/month