A fictional annual example shows why a change in one cost block does not transfer the same percentage to the entire budget.
Oldenburg, 9 October 2026. For the planning of a cleaning budget, three items must be distinguished: the starting total, the actual affected share, and the duration of the assumed change. Jonas Gebäudereinigung explains this distinction based on its existing public planning aid and a transparent model calculation. It does not describe a client order, a Jonas price, or any announced price change.
As a freely chosen starting point, twelve equal monthly amounts of 2.400 euros each are set. The annual budget is therefore 28.800 euros. For the example, an assumed 80 percent is attributed to a cost block that is to change; the remaining 20 percent remains unchanged. This share is a model assumption and not a measured industry value. In actual planning, its composition would first have to be substantiated.
The change initially affects a portion
If only the assumed 80 percent share increases by five percent, this results in an additional burden of 1.152 euros for a full year: 28.800 euros × 0,80 × 0,05. The total model budget rises to 29.952 euros. Relative to the starting total, this corresponds to four percent, because the unchanged portion receives no increase.
If five percent were calculated on the entire budget instead, it would result in an additional burden of 1.440 euros. This figure belongs to a different assumption, in which the entire starting total would be affected. Both calculations can therefore not be used interchangeably for the same cost allocation.
The period is added separately
If the intended change only applies to six of the twelve equally weighted months, the additional annual requirement is 576 euros: 28.800 euros × 0,80 × 0,05 × 6/12. The model budget for this year is then 29.376 euros. In a subsequent full year with the same assumptions, by contrast, 29.952 euros would be set again.
The half-year weighting is a separate calculation disclosed here. It is not an automatic sub-annual function of the Jonas workbook. In the case of seasonally different services or monthly costs of varying levels, the factor 6/12 would not be simply appropriate. Then the actual affected cost amount of the respective period would have to be used.
Documenting the basis for comparison
For a comprehensible comparison, the scope of service and quantities should initially remain the same. Changed cleaning areas, additional assignments, or one-off tasks change the starting point and must be reported separately. Anyone who combines price and quantity changes into a single percentage figure can no longer clearly identify their respective effects.
Documenting the initial position and scenario separately
A clear scenario calculation records the assumed change share, the rate of change, and the affected period alongside the starting total. The unchanged starting position is maintained for comparison. For each new assumption, it becomes clear which of these details was changed. A lack of proof for the share or the start of the change is an open planning issue. The calculation cannot replace it. This allows a model to be adapted later to actual data without presenting a merely assumed development as an already agreed cost change.
The public Jonas work aid contains example values and scenarios for changes to a cost share in the 'Budget' sheet. The explanation picks up on this existing calculation approach; it does not announce any new publication of the tool. All figures are fictional. A budgeted cost development does not in itself justify an agreed service price nor a claim to its adjustment. The article provides no tariff forecast or recommendation for a specific contract case.
Source on the existing work aid and its limits: Public Jonas work aid
About the sender
Jonas Gebäudereinigung is a cleaning company based in Oldenburg with a public service offering for commercial clients.
Contact
Jonas Gebäudereinigung
Alexanderstraße 101 B, 26121 Oldenburg, Germany
Telephone: 0441 24923021
Email: info@jonas-gebäudereinigung.de
Editorial note: This professional article was created with AI support based on the mentioned public Jonas work aid and the explicitly described explanation.