Tech debt calculator: what does waiting cost you every month?
Zinslast translates technical debt into the language of management, CFO and board: principal, monthly interest, effective annual rate and a repayment plan with break-even. No sign-up, your figures stay in your browser.
What the tool shows
“The system is old” becomes a figure in euros.
Engineering teams feel technical debt every day, but in the budget round they lack the figures. Zinslast converts each item into the measures management uses to judge a loan.
You enter
- +Team size, fully loaded cost per developer and productive hours
- +For each item: effort to remove it in person-days
- +Hours lost per month to workarounds and rework
- +Ongoing extra costs and risks with their probability
You get
- →Interest clock and tech debt balance sheet as a T-account by category
- →Effective annual rate and payback for each item
- →Repayment plan: three strategies compared, with break-even
- →One-page board paper with a proposed resolution
Method
How Zinslast calculates.
Every figure can be traced. The tool gives the formula for every number; here are the most important ones.
Calculation
- +Hourly rate = fully loaded cost per year ÷ (12 × productive hours per month)
- +Principal = person-days × 8 hours × hourly rate
- +Interest per month = hours lost × hourly rate + ongoing extra costs + expected loss ÷ 12
- +Effective annual rate = 12 × monthly interest ÷ principal
Assumptions and limits
- →Rough estimates are enough; every formula is disclosed in the tool
- →Interest grows at its own rate for each item left unpaid
- →Strategies: do nothing, highest interest first, smallest items first
- →A self-assessment, not an audit: it becomes reliable in a diagnosis
Example
Example: €85,458 interest a month.
The fictitious Nordwerk Software GmbH, with 42 developers, carries €579k of tech debt in ten items, from code copies for key accounts to an outdated Java runtime. It costs the company €85,458 a month, an effective annual rate of 177%. 10% of engineering capacity goes into workarounds instead of the product.
Frequently asked questions
Questions about Zinslast.
What is technical debt?
Technical debt is the shortcuts in software, architecture and operations that save time today and keep costing time and money later, like a loan that accrues interest. Zinslast makes that interest visible.
How accurate do my figures need to be?
Rough estimates are enough for the order of magnitude. Rating every item by the same logic matters more than precision. The tool shows the formula behind every figure.
Who sees my data?
Nobody but you. Zinslast calculates entirely in your browser: no server, no sign-up and no cookies. You can export your data as a file.
What do I do with the result?
The board paper sums up debt, interest and repayment plan on one page. In an initial call we review your assumptions and turn them into a reliable diagnosis with a roadmap.
How do you calculate the cost of technical debt?
For each item from two figures: the one-off effort to remove the debt (principal) and the ongoing cost while it remains (interest), i.e. lost working time, extra costs and expected losses. Zinslast converts both into euros using your hourly rate.
Can I share the result?
Yes. The board paper can be printed or saved as PDF. You export your data as a file; colleagues load it again in their own browser.
Reliable figures for your next board meeting.
In a free 30-minute initial call we review your assumptions and discuss how the self-assessment becomes a reliable diagnosis.