T&M vs fixed bid — which is better?

This is probably the most common argument on any contractor forum. Some contractors swear by time and materials. Others will not touch a job without a fixed bid. The honest answer is: it depends on the job. Here is how to decide.

time and materials: when it makes sense

T&M means you charge for your time and the client pays for materials separately. You get paid for every hour you work. Simple.

It works best when:

• The scope is unclear. Nobody knows what is behind that wall until you open it up. T&M means you are not gambling on what you find.
• The client keeps changing their mind. "Actually, can we move that outlet?" On T&M, no problem. On a fixed bid, that is a change order and an awkward conversation.
• It is service work by nature. Maintenance, repairs, punch list items. Jobs where you show up, see what needs doing, and fix it.
• You trust the client. T&M requires a good relationship. The client needs to believe you are working efficiently, not stretching the job.

The downside: your earnings are capped by hours in the day. You cannot benefit from being fast. And some clients will always wonder if the job could have been quicker.

fixed bid: when it wins

A fixed bid means you agree a total cost upfront. The client knows what they are paying. You know what you are earning — if you bid right.

It works best when:

• The scope is crystal clear. A kitchen remodel with specified cabinets, a bathroom to a drawn plan, a fence along a surveyed line. No surprises.
• You are competing on price. Most homeowners want to compare bids. That means fixed numbers. "It depends" does not win jobs.
• You are fast at this type of work. If you can do a job in three days that others take five, a fixed bid rewards your efficiency. T&M punishes it.
• The client demands it. Some clients — especially commercial ones — will only work with fixed bids. No bid, no job.

The downside: if you underbid, you eat the loss. And every surprise eats into your margin.

protecting yourself on a fixed bid

A fixed bid is riskier. That is not a reason to avoid it — it is a reason to bid it properly. This is where risk-adjusted estimation changes the game.

Instead of adding a flat 10% contingency and hoping for the best, you assign an uncertainty tier to each line item. Things you know are Certain or Low. Things you are less sure about are High or Wild Guess. The simulation then calculates exactly how much buffer you need — not too much, not too little.

Bid at P80 for standard fixed-price work. That gives you 80% confidence the actual cost stays below your bid. For high-stakes contracts with no change order mechanism, go to P95.

the hybrid approach

Smart contractors mix both. Here is how:

You do the first day or two on T&M. Open things up, see what you are dealing with. Then give a fixed bid for the main scope based on what you actually found — not what you guessed from outside.

Clients like this because they still get a fixed number for the big stuff. You like it because you are not gambling on unknowns. Everyone sleeps better.

the bottom line

T&M is safer for you but harder to sell. Fixed bids win more work but carry more risk. The hybrid approach splits the difference.

Whichever way you go, the bid still needs to be right. Build your estimate with honest uncertainty tiers and let the numbers tell you what to charge.