# Legacy ERP Parallel Run Cost Calculator

> Source: https://netray.co/tools/legacy-erp-parallel-run-cost-calculator
> Publisher: Netray (netray.co), AI and integration engineering for ERP and manufacturing systems.
> Section: Free Tools

## Short answer

Shows what each month of parallel running costs once you add legacy fees, double entry and reconciliation effort.

## Category

erp-migration

## Audience

- Project manager
- Controller
- CFO

## Tool

**Kind:** calculator

**Currency:** $

**Inputs:**

#### Parallel run length

**Key:** months

**Type:** slider

**Default:** 3

**Min:** 1

**Max:** 12

**Step:** 1

**Unit:** months

#### Legacy system monthly cost

**Key:** legacy_monthly

**Type:** number

**Default:** 18000

**Min:** 0

**Step:** 500

**Unit:** per month

**Help:** Licences, hosting, support and admin that continue during the overlap.

#### New system monthly cost

**Key:** new_monthly

**Type:** number

**Default:** 14000

**Min:** 0

**Step:** 500

**Unit:** per month

#### Staff doing double entry

**Key:** staff

**Type:** number

**Default:** 4

**Min:** 0

**Step:** 1

**Unit:** people

#### Double entry hours each

**Key:** staff_hours

**Type:** number

**Default:** 40

**Min:** 0

**Step:** 5

**Unit:** hours/month

#### Reconciliation hours

**Key:** recon_hours

**Type:** number

**Default:** 120

**Min:** 0

**Step:** 10

**Unit:** hours/month

#### Loaded hourly rate

**Key:** hourly

**Type:** number

**Default:** 45

**Min:** 0

**Step:** 5

**Unit:** per hour

**Outputs:**

#### Extra labour per month

**Key:** staff_month

**Expr:** (staff * staff_hours + recon_hours) * hourly

**Format:** currency

#### Incremental cost per month

**Key:** incremental_month

**Expr:** legacy_monthly + staff_month

**Format:** currency

**Description:** The new system would be paid anyway, so only legacy fees and labour are extra.

#### Total extra cost of parallel run

**Key:** total_extra

**Expr:** incremental_month * months

**Format:** currency

**Primary:** true

#### Total spend on both systems and labour

**Key:** total_all

**Expr:** (legacy_monthly + new_monthly + staff_month) * months

**Format:** currency

#### Extra cost per week of delay

**Key:** per_week

**Expr:** incremental_month * 12 / 52

**Format:** currency

**Primary:** true

**Chart:**

#### Extra cost vs parallel months

**Type:** bar

**X:** months

**From:** 1

**To:** 12

**Steps:** 12

**Series:**

- total_extra

**Disclaimer:** Planning estimate. Replace defaults with your contract and payroll figures.

## Content

**Intro:** A parallel run feels safe, but it keeps two systems alive and doubles some work. This calculator prices that safety so you can choose the shortest run that still protects you.

**Sections:**

#### How to use it

**Body:** Enter the legacy cost that cannot be cancelled during the overlap, such as licence terms, hosting and support. Add double entry only if users truly key transactions twice. If you load data nightly instead, set the staff to zero and put the checking time into reconciliation hours.

#### The method

**Body:** Incremental monthly cost equals legacy monthly cost plus extra labour. The new system cost is not incremental because it is spent regardless, though the tool shows total spend for reference. Total extra cost is incremental monthly cost times months, and the weekly figure shows what each slipped week costs.

#### Choosing a length

**Body:** Most teams need at least one full period close, often two. Parallel running past a clean quarter-end rarely adds assurance. Use the chart to see how the cost climbs per month and set an exit criterion such as three consecutive reconciled closes, rather than a calendar date alone.

**Bullets:**

- Define exit criteria first
- Cancel what you can early
- Negotiate short legacy extensions
- Automate reconciliation

**Cta:** Netray can build automated reconciliation between legacy and new ERP data so the run can be shorter. The calculator is independent of that.

**Faq:**

#### Is a parallel run mandatory?

**Answer:** No. Some companies cut over after rehearsals and keep the legacy system read-only. A parallel run suits high-risk financial processes, but it costs time and attention that rehearsals can often replace.

#### Why exclude the new system cost?

**Answer:** Because you will pay it whether or not you run in parallel. Only costs that exist because of the overlap belong in the incremental figure.

#### What does reconciliation cover?

**Answer:** Comparing trial balance, open AR and AP, inventory valuation and key reports between systems, and investigating differences.

#### How long should the legacy system stay readable?

**Answer:** Often for audit and tax retention periods, typically several years. See the data growth and archive calculator for storage planning.

## Search terms

erp parallel run cost, parallel run erp migration, dual running erp cost, gp parallel run business central, ax parallel run d365, erp cutover parallel period budget

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