Title: ERP vs MRP: The Difference Explained
URL: https://zudoworks.com/answers/erp-vs-mrp/
Description: ERP vs MRP for small manufacturers: MRP plans what to make and buy, ERP records everything around it. Which one a 10 to 50 person shop needs, explained.
Updated: 2026-11-03

# ERP vs MRP: what is the difference?

MRP, material requirements planning, is a calculation: from demand, bills of materials, stock on hand and lead times it works out what to make and buy, in what quantity, by when. ERP, enterprise resource planning, is the wider system that holds the records MRP needs and everything around them: purchasing, work orders, stock movements, costs, quality and accounts. Most manufacturing ERPs contain an MRP engine.

By Arunkumar V, CTO · 03 November 2026 · 3 min read

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- MRP vs ERP difference
- what is MRP software
- MRP system for small manufacturer
- do I need MRP or ERP

## What MRP does

MRP starts with what you need to ship and when. It explodes each finished item through its bill of materials to find the components, nets those against stock on hand and open orders, and offsets by lead time to produce a list of planned purchase orders and planned work orders with dates. The method dates from the 1960s and 1970s, when Joseph Orlicky and others formalised it for computer use. MRP is only as good as its inputs. A wrong stock balance, an outdated BOM or a guessed lead time produces confident but wrong suggestions. That is why a trustworthy stock ledger and current BOMs come before MRP, not after.

## What ERP adds

ERP holds the transactions that MRP reads and the ones it does not care about. It records the purchase order you raise, the receipt that puts stock on the shelf, the issue that takes it to a job, the labour logged at a work centre, the inspection, the invoice and the journal entries behind all of them. It also covers customers, vendors, roles and audit. The term was coined by Gartner in 1990 to describe MRP II systems that had expanded into finance and the rest of the business. In a small shop ERP, planning may be a reorder-point report rather than a full time-phased run, and that is often enough.

## Side by side

Some products sold as MRP software for small manufacturers are in practice light ERPs: they hold stock, BOMs, work orders and purchasing and connect to an accounting package. Others sold as ERP have weak planning. Look at what the product records, not the name.

| Aspect | MRP | ERP |
| --- | --- | --- |
| Purpose | Plan what to make and buy | Record and run the whole business |
| Core inputs | Demand, BOMs, stock, lead times | Every transaction, including planning |
| Output | Planned orders with dates | Stock, costs, accounts, quality, orders |
| Typical user | Planner or owner | Everyone from stores to accounts |
| Stands alone | Rarely, needs stock and BOM data | Yes, usually contains MRP |

## Which one a small shop needs

A 10 to 50 person shop almost never buys MRP on its own, because MRP without a live stock ledger and current BOMs produces noise. The sequence that works is: get stock movements recorded on the day, get BOMs to match what the floor actually builds, get work orders and purchasing flowing, then turn on planning. Reorder points handle most purchased parts; time-phased MRP matters more when lead times are long and demand is lumpy. If a vendor leads with the MRP run in a demo, ask to see the stock ledger and a job cost first.

## Where ZMOS fits

ZMOS is an ERP in this sense: it records stock movements in an immutable ledger with balances per warehouse, holds BOMs with revisions, scrap and cost roll-up, runs work orders with routing steps, and posts purchasing, quality and double-entry accounting in the same workspace. Planning for purchased parts is handled with reorder points per item. It suits sheet-metal, machining and fabrication shops of 10 to 50 people. If your main need is a full time-phased MRP run across long multi-level BOMs with capacity planning, confirm that in a demo with your own data before choosing it.

[What ZMOS does](https://zudoworks.com/zmos/)

- [stock control in ZMOS](https://zudoworks.com/zmos/inventory/)
- [BOM and production](https://zudoworks.com/zmos/production-and-bom/)
- [purchasing and reorder points](https://zudoworks.com/zmos/purchasing/)

## People also ask

Short answers, each one complete on its own.

### Related answers

- [What is a manufacturing ERP?](https://zudoworks.com/answers/what-is-a-manufacturing-erp/)
- [What is the difference between MRP and MRP II?](https://zudoworks.com/answers/mrp-vs-mrp-ii/)
- [What is the difference between ERP and MES?](https://zudoworks.com/answers/erp-vs-mes/)
- [How do I set reorder points for raw materials?](https://zudoworks.com/answers/how-to-set-reorder-points/)
- [How do I reduce material shortages on the shop floor?](https://zudoworks.com/answers/how-to-reduce-material-shortages/)
- [What is a bill of materials?](https://zudoworks.com/answers/what-is-a-bill-of-materials/)
- [All 54 answers](https://zudoworks.com/answers/)

### Inside ZMOS

[Zudo AI](https://zudoworks.com/zudo-ai/)[Stock ledger](https://zudoworks.com/zmos/stock-ledger/)[Low-code forms and rules](https://zudoworks.com/zmos/low-code/)[Barcode job cards](https://zudoworks.com/zmos/barcode-job-cards/)[Roles, audit log, API](https://zudoworks.com/zmos/roles-audit-api/)[Security](https://zudoworks.com/zmos/security/)[Free trial](https://zudoworks.com/zmos/free-trial/)[Why Zudo Works](https://zudoworks.com/why-zudo-works/)

Can I run MRP in a spreadsheet?

For a few products with shallow BOMs, yes, and many shops do. It breaks when stock balances in the sheet drift from reality, when BOMs change, or when more than one person edits it. The calculation is simple; keeping the inputs current is the hard part.

Is MRP the same as MRP II?

No. MRP plans materials. MRP II, manufacturing resource planning, added capacity, shop-floor control and financial links in the 1980s. ERP later extended that across the whole business. Most products today use MRP loosely for any planning function.

Does every manufacturing ERP include MRP?

Most include some planning, but the depth varies from a reorder-point report to a full time-phased run with capacity checks. Ask the vendor to run planning on your own BOMs and demand during the demo and to explain each suggested order.

Which should I buy first, MRP or ERP?

Buy the system that records stock, BOMs and work orders accurately. Planning only works on top of trustworthy records. For most small shops that means a manufacturing ERP with reorder points, adding time-phased MRP once the data is clean.