---
title: "Room-by-Room Budget for Interior Design: How to Split It"
date: 2026-10-22
lang: en
url: https://archiboard.design/blog/room-by-room-budget-interior-design
---

# Room-by-Room Budget for Interior Design: How to Split It

A room by room budget for interior design works like this: fix the total, set aside a contingency and the shared costs, then divide what remains between rooms by their weight in the project. After that, assign every estimate item to a room, or split it between rooms by a clear rule. This article shows the method step by step, with an example you can copy.

## Why a room budget works better than one total

A single project total tells you only when you are over budget, not where. A client who approves a sofa, a rug and a lamp one by one can spend the living room allowance before the kitchen is even specified. When every room has its own limit, you see the problem at the moment of the decision, not at the end of procurement.

A room budget also helps the conversation with the client. People think in rooms: "the bathroom is where we spend more, the hallway is where we save." Turning that into numbers early prevents arguments later.

### What a room budget does not cover

Some costs do not belong to any single room: the studio fee, project-wide delivery, services that serve the whole home, and the contingency. If you force them into rooms, the room numbers become unreliable. Keep them as separate lines and decide deliberately which of them you will split (see section three).

## Step 1: Build the budget frame

Start from the top and work down. The order matters, because each step reduces the amount available for rooms.

1. **Fix the approved total.** Use the amount the client has actually agreed to spend, in client prices, not your purchase prices.
2. **Reserve a contingency.** Many designers hold back a percentage for price changes, replacements and surprises found on site. Choose a figure with the client and keep it visible as its own line.
3. **Take out shared costs.** Studio fee, project-wide delivery, services and any item you will not assign to one room.
4. **List the rooms.** Include every space that will receive items: hallway, storage, balcony and terrace are often forgotten.
5. **Allocate the remainder to rooms.** Use weights, described below.
6. **Get the client to approve the room limits,** not only the total.

### How to weigh the rooms

Area alone is a poor guide. A small bathroom with sanitary ware, tiles, plumbing fixtures and a custom vanity can cost more per square metre than a large living room. Combine three factors: area, expected finish level and the number of expensive items such as built-in furniture, sanitary ware, appliances and lighting. Then adjust by hand and check the result per square metre.

### Example allocation

The figures below are an illustration, not a benchmark. Total approved budget: EUR 100,000. Contingency: EUR 8,000. Shared costs: EUR 12,000. Left for rooms: EUR 80,000.

| Room | Area, m² | Share of room budget | Budget, EUR | EUR per m² |
| --- | --- | --- | --- | --- |
| Kitchen | 14 | 27.5% | 22,000 | 1,571 |
| Living room | 32 | 25% | 20,000 | 625 |
| Primary bedroom | 18 | 15% | 12,000 | 667 |
| Bathroom | 8 | 15% | 12,000 | 1,500 |
| Children's room | 12 | 10% | 8,000 | 667 |
| Hallway | 9 | 7.5% | 6,000 | 667 |
| **Total for rooms** | 93 | 100% | **80,000** | 860 |

The per-square-metre column is a sanity check. If the living room looks cheap next to the kitchen, ask whether the client really wants that, or whether the kitchen figure is inflated by appliances that could be a separate line.

## Step 2: Assign every item to a room

A room budget is only as accurate as the room tags on the estimate. Most errors come from items that are untagged or tagged to the wrong room. Work through the estimate once, carefully, and then keep the rule that no item enters the estimate without a room.

1. Export or collect the full list of items, including those still in the proposal stage.
2. Tag each item with a room. If an item has no clear room, put it in a temporary "unassigned" group and clear that group before the next client meeting.
3. Check that built-in items (wardrobes, kitchen units, wall panels) sit in the room where they are installed, not where they are stored in the workshop.
4. Add the quantity you actually buy: whole packs, reserve for cutting, spare pieces. A tile budget based on net area will always be short.
5. Compare each room total with its limit and mark rooms that are already above 90% of the limit while many items are still undecided.

For flooring, tiles and paint, calculate quantities per room before pricing. A [material calculator](/tools/material-calculator) helps you move from room area to packs and reserve without manual arithmetic.

### Checklist before you present room limits

- Every room that receives items is on the list.
- The sum of the room areas matches the project area, or the difference is explained.
- No item is left without a room.
- Contingency and shared costs are separate lines, not hidden inside rooms.
- Quantities include reserve and whole packs.
- The client has seen the limits in client prices, not purchase prices.

## Step 3: Split items that serve several rooms

One floor covering runs through three rooms. The same lamp hangs in two bedrooms. Delivery is one invoice for the whole order. Decide the splitting rule once, write it down, and apply it consistently, so the room numbers can be explained to the client.

| Cost type | Suggested split rule | Reason |
| --- | --- | --- |
| Flooring or paint used in several rooms | By area of each room | Cost follows the surface covered |
| Identical fixtures (same lamp, same socket set) | By quantity in each room | Each room consumes the number of pieces it gets |
| One lot with a custom split (a shared stone slab, a batch of tiles) | By percent, agreed manually | Usage is uneven and known in advance |
| Delivery of one order | In proportion to the value of items per room, or kept as a shared line | Avoids distorting small rooms |
| Studio fee, project coordination | Keep as a shared line | Not tied to any space |
| Contingency | Keep as a shared line | Moves to the room where the problem appears |

### Keep one purchase as one purchase

Splitting a cost between rooms must not turn one purchase into several. You still place one order, receive one invoice and make one supplier payment. Only the budget view is divided. If your spreadsheet duplicates the row for every room, payments and quantities quickly stop matching the supplier documents.

### Odd quantities

When 68 pieces go into two rooms, the split is 34 and 34. When the number is odd, decide in advance which room takes the extra piece and keep that rule the same throughout the project. Small inconsistencies like this are what make a room table hard to trust.

## Step 4: Track, rebalance and report

A room budget is a working tool, not a one-off table. Review it on a fixed rhythm, for example every week during specification and after every large approval during procurement.

1. **Separate proposed from approved.** For each room, track two totals: everything proposed, and only what the client has agreed. The first shows risk, the second shows commitment.
2. **Calculate what is left.** Room limit minus approved items equals the remaining amount. Compare it with the proposed total to see whether the open items still fit.
3. **Flag rooms by status.** Within the limit, close to the limit, over the limit.
4. **Rebalance only with the client's consent.** If the kitchen goes over, decide whether to cut items there, take money from the hallway or use the contingency. Record the decision and the new limits.
5. **Report in rooms.** Send the client a short summary: limit, approved, left, for each room.

### Example of a room status review

Illustrative figures in EUR for the kitchen from the earlier example.

| Room | Limit | Approved | Proposed, not yet approved | Left after approved | Status |
| --- | --- | --- | --- | --- | --- |
| Kitchen | 22,000 | 15,500 | 8,200 | 6,500 | Over limit by 1,700 if all proposals are approved |
| Living room | 20,000 | 9,000 | 7,500 | 11,000 | Within limit |
| Hallway | 6,000 | 5,400 | 0 | 600 | Close to limit |

The kitchen is the interesting row. Approved spending is still under the limit, but the open proposals would push the room over. This is the moment to offer a cheaper alternative for one or two items, before the client falls in love with the expensive option.

### Weekly review checklist

- New items from the last week all have a room.
- Prices changed by suppliers are updated.
- Rejected items are excluded from room totals.
- Rooms near their limit have an action: alternative, reduction or a budget conversation.
- Any transfer between rooms is recorded with a date and the client's approval.
- Contingency use is visible as a separate number.

If you also track what the client has paid and what you owe suppliers, keep that on a separate layer from room limits. Room budgets answer the question "how much can we spend here"; [project finance](/features/project-finance) answers "how much has actually moved".

## How to do it in ArchiBoard

1. Open the project and go to **Rooms** → **Add room**. Create every room that will get items. The room card shows **Budgeted**, **Left** or **Over budget**. If the sum of room areas does not match the project area, a warning appears.
2. Open **Project Finances** and enter the approved budget. The budget can be allocated by room, so overspending per room is visible there as well.
3. Go to **Estimates** and press **Add item** in the right room. Paste a product link and press **Auto-fill**, check the fields, then **Save item**.
4. For an item that serves several rooms, press **Add item** above the estimate and turn on **In several rooms**. Tick the rooms and choose **Evenly**, **By quantity** or **By percent**. It stays one item, with one purchase and one payment. Adjust exact quantities later with **Split across rooms** in the item row.
5. Set **Group by** to **By room** to see totals for each room. Items without a room appear in the **No room** block, where you can distribute them.
6. Switch between **Preliminary** and **Approved** to compare everything proposed with what the client agreed. Use **Economics** mode for your own margin view and **Specification** for a view without internal finances.
7. To send the client one room, press **Export to PDF**, leave only that room in **Rooms**, then **Download PDF**.

More about the estimate screen: [estimates in ArchiBoard](/features/estimates) and the [help chapter on estimates](/help/estimates).

## FAQ

### How much contingency should a room budget include?

There is no universal figure. It depends on how many items are still undefined, how reliable your suppliers are and how much of the work is custom. Choose a percentage with the client, show it as a separate line and describe what it may be used for, so it does not look like a hidden margin.

### Should the studio fee be split between rooms?

In most cases keep it as a shared line. Splitting it makes room numbers look larger and mixes design work with purchases. If the client wants one price per room, split it by room budget share and say so clearly in the document, so both figures can be reconciled with the contract.

### What if the client wants to move money from one room to another?

Allow it, but make it a recorded decision. Write down which room loses budget, which gains it and which items are affected. Then update the limits and send the client the new summary. Without a record, the budget quietly drifts and nobody can explain later why the hallway ended up so cheap.

### How do I budget a room that is not designed yet?

Use a placeholder limit based on area, finish level and a few known big items, and mark the room as provisional. Revisit it when the concept is approved. A rough limit is better than none, because it still protects the rooms that are already specified from absorbing the remaining money.

### Should room budgets include purchase prices or client prices?

Use client prices, because the limit is what the client agreed to spend. Track purchase prices and margin separately for your own profit calculation. Mixing the two makes rooms look cheaper than they are for the client and hides how much the studio actually earns on each room.