Planner

DIY project planner with budget and time buffer

Most DIY jobs cost more and take longer than the first guess. Enter your estimates, choose how much buffer to add, and see a planned budget, planned hours and the number of work sessions. Everything is worked out on this page, and nothing is saved or sent.

$357 planned budget

Worked example (shown when scripts are off): $250 of materials and $60 of tools make a $310 base. A 15 percent buffer adds $46.50, so plan for about $357. Eight estimated hours plus a 40 percent buffer is 11.2 hours, or 3 sessions of 4 hours.

Before you decide

If the planned total is more than you want to spend, change the project rather than the buffer. Cut the scope, borrow or rent a tool, or split the job into stages. If the planned hours do not fit the weekend, plan for two weekends instead of rushing the last step.

The rule in words

Base cost is materials plus tools you have to buy plus any paid help or rentals. The budget buffer is that base cost multiplied by your buffer percent. Planned budget is the base plus the buffer. Planned hours are your estimate multiplied by one plus the time buffer, and the number of sessions is the planned hours divided by the hours per session, rounded up.

If you enter a spending limit, the planner compares it two ways. It tells you whether the base cost fits, and whether the cost with the buffer fits. A base that fits but a total that does not is a useful warning: you can afford the plan only if nothing goes wrong, so decide now what you would drop.

Choosing the buffers

The defaults of 15 percent for money and 40 percent for time are our starting points, not published standards. There is no official figure for a DIY project, and the right amount depends on the job. As a rough guide, use less for a task you have done before with every material priced, and more for a first attempt, an older house where surprises are likelier, or work that opens up a wall or floor. Time tends to slip more than cost, which is why the default time buffer is higher.

What to put in each box

Materials. Price every item on your list, including fixings, tape, sandpaper, drop cloths and disposal. Small items are what usually get missed.
Tools you must buy. Only count tools you do not already own. If a tool will be used once, compare renting or borrowing.
Paid help or rentals. Include licensed trades for anything electrical, gas, structural or plumbing that you should not do yourself.
Hours. Include preparation, cleanup, shopping trips and drying times you have to wait for, not just the visible work.

Limits

This is a planning aid, not a quote. It does not know your local prices, whether your job needs a permit, or whether hidden damage is waiting behind the surface. Check local rules and the instructions that come with each product. If a job involves wiring, gas, structure or major plumbing, get a licensed professional to assess it before you set a budget. This page is general information, not professional advice.

Where this comes from

The calculation is plain arithmetic. Keeping a contingency for unexpected costs is a widely used planning habit in home projects, but we did not find a published standard percentage for small DIY jobs, so the defaults here are our own and you should change them. The code was run against 15 or more sample combinations, including zero values and extreme inputs, and the results were compared with hand calculations.