Your team

Example value, the team size the Smashing formula assumes. Source: Speicher and Baena Wehrmann, Smashing Magazine, 2022.

Example value, the team size the Smashing formula assumes. Source: Speicher and Baena Wehrmann, Smashing Magazine, 2022.

Example value. A product is one app or codebase.

Example value. Use your own loaded hourly cost.

Example value.

Example value.

Drift: work done twice

Example value. No published study measures this; ask your team.

Decay: keeping products current

Example value.

Example value. Include fixing what the upgrade breaks.

Example value. Figma's library analytics and a code audit give real counts.

Example value.

Maintenance load

Average team size at companies of 100 to 499 people. Source: zeroheight Design Systems Report 2025.

Example value. No published study measures this.

What the system returns when it is used

The average of three published figures; Figma's 34% is called the maximum. Source: Speicher and Baena Wehrmann, Smashing Magazine, 2022.

The average of three published figures, including Sparkbox's one-form study. Source: Speicher and Baena Wehrmann, Smashing Magazine, 2022.

Example value. Lower it if your system covers little of your interface.

The authors of the Smashing formula suggest reporting about ±25%. Source: Speicher and Baena Wehrmann, Smashing Magazine, 2022.

Your estimate, from your inputs

Drift, a year
83,000 to 140,000about 1,800 hours
Decay, a year
8,600 to 14,000about 190 hours
Maintenance load, a year
130,000 to 220,000about 2,900 hours
Yearly cost of drift, decay and maintenance
220,000 to 370,000drift and decay take about 3% of the product team's hours
Clearing the backlog, once
4,100 to 6,800about 90 hours
Value when the system is used, a year
540,000 to 900,000time given back, at the cited rates
Running cost, a year
330,000 to 550,000the system team
Return on what the system costs
-23% to 110%after drift and decay; below 0% the system costs more than it returns

Amounts are in the currency of your hourly cost, rounded to two figures and shown as a range. This is your estimate from your own numbers, not a claim by Loom. The value line uses published averages from small studies; replace them with your own measurements when you have them.

The formula

Drift
(D + E) × r × W × Cevery person who builds interface, times the hours a week they spend redoing or reconciling, times the weeks and the hourly cost
Decay
P × R × m × Ceach product taking up each release
Maintenance load
T × H × W × s × Cthe system team's reactive share
Backlog (one-off)
x × f × Cclearing what has already drifted
Yearly cost of drift, decay and maintenance
Drift + Decay + Maintenance load
Value when the system is used
(D × Zd + E × Ze) × u × H × W × Cthe time a working system gives back, on the share of work it covers
Running cost
T × H × W × Cthe system team
Return
(Value − (Running cost + Drift + Decay)) ÷ (Running cost + Drift + Decay)drift and decay count as costs because they are work the system was meant to remove
Range
each figure × (1 ± range); the return pairs low value with high cost, and the reverse
What each symbol means
  • D product designers who use the system
  • E engineers who build product interface
  • P products that consume the system
  • C cost of one working hour
  • W working weeks a year
  • H working hours a week
  • r hours per person per week spent rebuilding what exists or reconciling Figma and code
  • R system releases a year that products must take up
  • m hours per product to take up one release
  • x known detaches, local copies or open exceptions
  • f hours to resolve one of them
  • T people on the design-system team
  • s share of the system team's time spent on support, fixes and chasing drift
  • Zd time saved by designers on work the system covers
  • Ze time saved by engineers on work the system covers
  • u share of the week spent on work the system covers
  • ± uncertainty range