user guide

User Guide – HOAI Calculator

1. Overview

The HOAI Calculator is an iOS app for fast and practical calculation of fee estimates and service phase allocations based on the HOAI concept. The app is intended in particular for specialist planners, engineering offices, consultants, project managers, and anyone who needs to prepare fee proposals, initial budget assessments, or structured service phase overviews.

Depending on the selected mode, the HOAI Calculator can:

• distribute service phases by percentage,

• determine a fee based on table values,

• process area-based input in hectares,

• include surcharges, discounts, and incidental expenses,

• export and share results as a PDF,

• store projects and the latest input values.

The app works primarily with net values. An optional gross display is added only at the end of the calculation.

2. Launching the App

When opening the app, a short splash screen appears first. After that, you are taken directly to the main view of the HOAI Calculator.

In the main view you will find:

• the selection of the service profile,

• the selection of the calculation mode,

• input fields for costs, zone, rate, or area,

• editable service phases,

• the results section,

• the menu at the top right via the three-dot icon.

3. Operating Modes

The HOAI Calculator provides several modes. You can switch between them depending on the task at hand.

Mode A – Distribution

This mode is used for the pure distribution of a total amount across service phases 1 to 9.

Purpose

Mode A is useful when a total amount or fee basis already exists and needs to be distributed across the individual service phases using the HOAI percentage shares.

Input

• chargeable costs or reference amount

• selected service profile

• percentage values of the service phases

Output

The app calculates for each service phase:

• the stored percentage share,

• the allocated net amount,

• the total sum.

Typical Use Cases

• allocating a known total fee across service phases 1–9

• reviewing partial appointments

• creating an initial proposal structure

Mode B – Fee Calculation

This mode reflects the classic fee calculation based on the fee table.

Purpose

Mode B is used when a fee is to be derived from chargeable costs, fee zone, and selected rate.

Input

• chargeable costs net

• service profile

• fee zone

• rate selection

• optional: conversion/renovation surcharge

• optional: discount

• optional: incidental expenses

Calculation Basis

The app uses the table range of the selected service profile and displays:

• Table value from … to …

• based on that, the selected rate:

• lower rate

• middle rate

• upper rate

Output

The app displays, among other things:

• base fee for basic services, net

• surcharges

• discount

• incidental expenses

• final result, net

• optionally VAT and total gross amount

Typical Use Cases

• preparing fee proposals

• previewing fee levels

• comparing different zones or rates

• determining fee approaches for project phases

Mode C – Area / Hectare Mode

Mode C is intended for calculations where area values in hectares are used as the basis.

Purpose

This mode is suitable for service profiles or application cases where the calculation is not primarily based on chargeable costs, but on area-based values.

Input

• area in hectares

• additional mode-specific values depending on the selected calculation basis

Output

The app determines the relevant result based on the area input and presents the data in a similarly structured format.

Note

Depending on the project type and selected service profile, the input fields, labels, and result presentation may differ from Mode A and Mode B.

4. Service Profiles and Presets

The HOAI Calculator provides predefined presets for typical service profiles. These act as practical starting values and can be changed at any time.

Typical presets include, for example:

• Buildings

• MEP / Electrical Engineering

Once a preset is selected, the app loads the corresponding default percentage values for the service phases. These values remain fully editable.

Advantages of Presets

• fast start without manually entering all base values

• common distributions available immediately

• still flexible for project-specific or contractual adjustments

5. Entering Chargeable Costs

In Mode A and Mode B, calculations are generally based on chargeable costs net.

How the Input Works

• Enter the required amount in the cost field.

• The input is always a net value.

• Numeric fields are intentionally right-aligned in the app so that larger amounts remain easy to read.

Default and Reset Value

When the app starts or after a full reset, the default amount is €25,000.

6. Fee Zone and Rate

In Fee Calculation mode, you also select:

• the fee zone,

• the rate.

Fee Zone

The fee zone influences the table range and therefore the resulting fee. Depending on the selected service profile, the relevant zones are available.

Rate

The rate is processed in the app as a selection within the fee table range. Typical options are:

• Lower rate

• Middle rate

• Upper rate

The output shows this transparently, for example:

Rate: Middle rate (50%) → Fee: €29,511 net

7. Editing Service Phases 1–9

A key feature of the app is the editing of service phase percentages.

What Can Be Adjusted

You can enter an individual percentage value for each service phase.

Properties of the Percentage Fields

• directly editable in the list

• maximum of one decimal place

• immediate recalculation after every change

Typical Use Cases

• project-specific deviations from standard values

• partial commissioning

• office-specific internal standards

• mapping a specific contractual arrangement

8. Tool: “Set to 100%”

The “Set to 100%” function normalizes the currently entered service phase values so that their total becomes exactly 100%.

Purpose of the Function

If percentage values have been changed manually and no longer total exactly 100%, the distribution can be corrected automatically.

Result

• the existing proportions are preserved as far as possible

• the total is adjusted to 100%

9. Tool: “Reset”

Using “Reset”, the app returns to defined default values.

The Following Values Are Reset in Particular

• costs to €25,000

• fee zone to Zone I

• rate to Lower rate

• service phases to the default values of the selected preset

• surcharges and additional values to their default settings

When a Reset Makes Sense

• before starting a new calculation

• when switching projects

• when returning to a clean starting point

10. Surcharges and Further Adjustments

In Fee Calculation mode, additional values can be taken into account.

Conversion / Renovation Surcharge

The conversion surcharge in percent is added to the base fee.

Example:

• base fee net: €10,000

• conversion surcharge: 20%

• result: €12,000 net before further adjustments

Discount

The discount in percent is applied at the end to the calculated fee.

Important:

• the discount does not apply to construction costs,

• the discount is not automatically distributed to the individual service phases,

• it affects the final fee result.

Incidental Expenses

Incidental expenses are shown as a percentage-based surcharge in the results block.

Important:

• incidental expenses are treated as a net surcharge,

• they are not artificially spread across each individual service phase line,

• this keeps the structure clear and easy to understand.

11. Net and Gross Display

The app calculates net values by default.

Standard Display

All intermediate values and service phase amounts are shown as net amounts.

Option: “Show Gross”

Via the corresponding setting, you can activate an additional gross display.

In that case, the results section also shows at the end:

• VAT

• total gross amount

Important

• the individual service phase lines still show net values only,

• incidental expenses remain net,

• the gross display is only intended for the final total.

12. Notice for Low Costs in Technical Equipment Calculations

In certain cases, the app displays a professional guidance note.

Case

If calculations in the Technical Equipment area are performed in Fee Calculation mode with chargeable costs below €25,000, the app shows a notice.

Meaning

The reference tables in this area begin at €25,000. Below that threshold, other fee arrangements are usually more appropriate in practice, for example:

• lump-sum fees

• hourly rates

• project-specific fixed fees

This notice helps with plausibility checks and prevents misleading interpretations.

13. Understanding the Results Block

The results block is clearly structured and visually separated from the input section.

Typical Structure

• total summary

• divider line

• result rows with fee components

• optional VAT and gross total at the end

Possible Content

• fee for basic services

• conversion surcharge

• discount

• incidental expenses

• total net fee

• VAT

• total gross fee

The presentation is intentionally designed so that it remains easy to read both inside the app and in the exported PDF.

14. Saving Projects and Storing Recent Entries

The app stores various inputs so that you can continue working quickly the next time you open it.

Typically Stored Values

• last selected mode

• selected service profile

• costs

• fee zone and rate

• service phase percentages

• conversion surcharge, discount, incidental expenses

• gross toggle and VAT rate

• company data and project defaults

Advantages

• less repeated data entry

• fast continuation of ongoing work

• consistent day-to-day office use

15. Creating and Sharing a PDF

Using the “Create & Share PDF” function, the current calculation can be exported as a proposal or calculation document.

PDF Content

Depending on the selected settings and mode, the PDF may include:

• company data

• project name

• proposal number

• service profile

• selected mode

• list of service phases with net amounts

• results block with totals

• optional VAT and gross total at the end

Typical Use Cases

• sending proposals

• internal review

• documentation

• project filing

• coordination with clients or partners

Sharing the PDF

After creation, the PDF can be shared directly via the standard sharing function of the iPhone or iPad, for example through:

• email

• Files app

• messages

• AirDrop

16. Menu and Navigation

At the top right of the main screen, you will find the three-dot menu.

From there, you can open additional app sections such as:

• Reports / Evaluations

• Help

• Settings

• Legal Information

These sections open as clean overlay views.

17. Settings

The settings area allows you to manage app-wide defaults and personal preferences.

Possible Settings Content

• company data

• default project information

• gross display

• VAT rate

• diagnostic or support functions

• further user-specific defaults

Operation

• X: close without saving

• ✓: save and apply

This ensures that changes can be accepted in a controlled way.

18. Help and Support

The help section provides support for using the app.

Contact Support

Using the corresponding button, a support email can be prepared automatically.

The recipient, subject line, and text are prefilled.

Copy Log

If available, a diagnostic log or settings log can also be copied to support troubleshooting more efficiently.

19. Typical Workflow

A common workflow in the HOAI Calculator looks like this:

1. Open the app

2. Select the service profile

3. Choose the mode

4. Enter costs or area

5. Define fee zone and rate if required

6. Review or adjust the service phases

7. Enter surcharges, discount, and incidental expenses

8. Review the result

9. optionally activate the gross display

10. create and share the PDF

This workflow is suitable both for early fee assessments and for preparing proposals.

20. Practical Notes for Daily Use

For Proposal Calculations

Before sending a proposal, check in particular:

• the correct service profile,

• the appropriate fee zone,

• the completeness of the commissioned service phases,

• surcharges and incidental expenses,

• the correct net / gross presentation.

For Internal Calculations

The app is very well suited for:

• quick comparison calculations,

• variant studies,

• fee estimations in early project stages,

• structured preparation for client meetings.

For Partial Appointments

If not all service phases are commissioned, the percentage values can be reduced accordingly or only selected service phases can be included.

21. Frequently Asked Questions

Why are only net values shown in the service phase lines?

Because the app deliberately follows a clear net-based structure. VAT is only added at the end if the gross option is enabled.

Why do notices appear for low cost values?

Because certain table or guidance ranges only become meaningful above defined minimum thresholds.

Can I change the service phase percentages freely?

Yes. The preset default values are only a starting point.

Can I continue using the data elsewhere?

Yes. The results can be exported as a PDF and shared.

22. Summary

The HOAI Calculator is a practical tool for quick, clear, and structured calculation of fees and service phase distributions. With multiple modes, editable service phases, surcharge logic, net/gross output, project persistence, and PDF export, the app supports both internal project work and external proposal communication.

The combination of simple operation and professionally structured presentation makes the HOAI Calculator a useful tool in everyday planning and office practice.

23. Website Notice

This user guide describes the core functions of the HOAI Calculator in its current basic structure. Depending on the app version, individual functions may be extended, refined, or adjusted.

Further information, support, and updates are available through the official contact and information channels of SchelloLabs.

APPS MADE IN PETERSFEHN - GERMANY