How to Read and Compare Contractor Bids
Getting bids back from contractors is one of those moments that feels like progress until you actually sit down to read them. Suddenly you're staring at documents that look nothing alike, use terms you've never heard, and land at numbers that are thousands of dollars apart.
This is also the moment where a lot of renovations quietly go wrong, because most clients don't yet have the tools to evaluate what they've been given. This guide will walk you through exactly what you're looking at and how to make sense of it before you commit to anything.
This post is part of our series on navigating the construction bidding process. Before you dive in: Why You Should Hire Your Interior Designer Before Your Contractor
The series:
1. How to Read and Compare Contractor Bids
2. Why Your Designer Should Set Your Renovation Allowances Before Contractors Bid
3. What to Ask a Contractor Before You Sign
4. Pre-Construction: What It Is and Why It Matter
Start With Three Bids
Before getting into how to read a bid, it's worth addressing how many to collect. Three is the standard, and there are good reasons for it.
One bid gives you a number with no context. You have no way of knowing whether it's fair, inflated, or missing half the scope. Two bids give you a comparison, but if they diverge significantly you still can't tell which one is the outlier. Three bids give you enough data to identify a reasonable range, spot the outlier in either direction, and make an informed decision.
More than three bids can work against you. Contractors invest real time in preparing detailed estimates, and the ones worth hiring know their value. Asking five or six contractors to bid on a project signals that price is your primary criterion, which tends to attract contractors who compete on price rather than quality. Three well-chosen contractors is the right number for most residential projects.
Bid, Estimate, Proposal: What's the Difference?
Some contractors use these terms interchangeably, but they don't mean the same thing, and the distinction matters.
A bid is generally a fixed price for a defined scope of work. A proposal is similar but often includes more detail about approach and process. An estimate is approximate, meaning the contractor is giving you their best projection, not a committed number.
If you think you have a fixed price but the contractor considers it an estimate, you'll find out the hard way once the project is underway. Before you sign anything, ask directly: is this a fixed-price contract or is the final number subject to change?
Why Bids Are Rarely Comparing the Same Thing
When contractors bid independently without a standardized set of documents to price against, they each make their own assumptions about scope, materials, and finish level. One contractor includes permits. Another excludes them. One prices tile at $12/sf while another assumes $25/sf. One includes a project manager on site daily. Another assumes the owner will coordinate directly with subcontractors.
None of this is necessarily dishonest. It's the natural result of asking different people to interpret the same general brief without specific guidance. The problem is that when you line up the totals, you're comparing documents that reflect different projects.
This is the core argument for having a designer involved before bids go out. A designer can provide a standardized set of allowances, a clear scope, and specific finish expectations that every contractor prices against. The result is bids that are actually comparable. Without that foundation, the comparison work falls entirely to you.
What to Look For in Each Bid
Read every bid in full before you look at the total. You're trying to understand what each contractor is and isn't including before the numbers mean anything. Here are the sections that matter most.
Scope of work. This is the written description of what the contractor is agreeing to do. Read it carefully. If something you discussed isn't mentioned here, assume it isn't included. Verbal conversations don't make it into the budget unless they make it into the scope.
Line items. These are the individual cost breakdowns: demolition, framing, plumbing, electrical, tile work, painting, and so on. A detailed line-item bid gives you visibility into where the money is going and makes comparison meaningful. A lump-sum bid that says "kitchen renovation: $95,000" with nothing behind it tells you very little.
Allowances. These are placeholder numbers for materials and products not yet selected, things like tile, fixtures, appliances, and hardware. They deserve close attention, and there's more on them below.
Exclusions. This section is just as important as what's included. Exclusions are the things the contractor is explicitly not pricing. Permits, design fees, specialty installations, and temporary housing often appear here. A bid that looks competitive sometimes looks that way because the exclusions list is long.
Payment schedule. This outlines when payments are due, typically tied to project milestones. A contractor asking for a very large deposit upfront, particularly above 10 to 15 percent, is a yellow flag worth noting.
Timeline. Not all bids include a projected timeline, but the ones that do give you useful information both about the project and about how organized the contractor is.
The Allowance Problem
Allowances are where budgets most commonly come apart, and they deserve their own scrutiny. When you receive a bid, look at every allowance line and ask whether the number is realistic for the finish level you're expecting.
A tile allowance of $8/sf might work for a laundry room. It won't work for a primary bathroom with handmade tile. If the allowances in the bid don't reflect the actual design direction, the total number is not a reliable budget. It's an optimistic estimate that will grow once real selections are made.
To see how much this matters, consider a simple example. You're renovating a kitchen and two contractors each price tile, fixtures, and appliances. Contractor A comes in at $175,000. Contractor B comes in at $195,000. But when you pull the allowances:
Contractor A: tile at $10/sf, fixtures at $1,200, appliances at $8,000 Contractor B: tile at $22/sf, fixtures at $3,500, appliances at $15,000
If your actual selections land closer to Contractor B's assumptions, the $20,000 gap between the bids disappears entirely and then some. Contractor A wasn't cheaper. Their allowances just didn't reflect your project.
This is why normalizing allowances before comparing totals is essential. Pick the number that actually reflects your design direction, apply it consistently across all bids, and recalculate. The results will be far more meaningful than the total on the cover page.
Lump Sum vs. Cost-Plus
Most residential bids are lump sum, meaning the contractor gives you a fixed price for the agreed scope. But some contractors work on a cost-plus basis, meaning they charge you their actual costs plus a percentage or flat fee for overhead and profit.
Cost-plus arrangements can work well with the right contractor. They tend to attract more transparent contractors, since there's no incentive to cut corners to protect a fixed margin. On complex projects with significant unknowns, they can also result in lower total costs than a lump-sum contractor who prices in heavy contingency to cover uncertainty.
The tradeoff is that you carry more financial risk, and you need to be actively engaged in monitoring costs throughout the project. If you're considering a cost-plus contractor alongside lump-sum bids, ask them to provide a detailed cost estimate so you have a number to work with. You can't compare a cost-plus proposal to a lump-sum bid on the same terms, but you can at least understand what you're looking at.
What's Often Missing
Even detailed bids tend to leave things out. Common omissions include permit fees, structural engineering if it's needed, temporary housing or storage if you'll need to vacate, utility disconnection and reconnection, debris removal, and anything related to unforeseen conditions. In an older Boston home, unforeseen conditions are rarely nothing. A phrase like "additional work due to unforeseen conditions will be billed at time and materials" is standard and reasonable, but worth understanding before you sign.
A Note on Change Orders
A change order is a formal amendment to the contract that adjusts scope, cost, or timeline once work has begun. Some change orders are unavoidable, the result of genuine surprises behind walls or shifting client decisions mid-project. But change orders are also where underbid projects make up their margin.
A contractor who wins the job on an aggressive number and then generates frequent change orders for work that should have been in the original scope is a recognizable pattern. The best protection is a detailed, well-written scope at the outset and a contractor whose bid reflects that scope honestly. If you find yourself asking why something obvious isn't included in the original bid, trust that instinct before you sign.
Building a Comparison Sheet
Once you've read every bid in full, build a simple side-by-side document. List every line item, every allowance, and every exclusion from every bid in one place. Note where contractors have priced the same thing differently and where things appear in one bid but not others. Normalize the allowances. Account for the exclusions. Then look at the totals.
It takes time, but it transforms a confusing stack of documents into an actual comparison. It also gives you a precise list of questions to bring back to each contractor before you make a decision.
When One Bid Comes in Much Lower
If one bid is significantly lower than the others after you've normalized allowances and accounted for exclusions, go back and find out exactly why. Ask the contractor to walk you through their scope line by line. There may be a legitimate explanation, but there may also be something missing that will surface later as a change order.
The goal isn't to dismiss low bids. It's to understand them. A bid you understand is a bid you can evaluate. A bid you don't understand is a risk.
Check References Before You Decide
The comparison sheet will tell you a lot, but it won't tell you everything. Before you make a final decision, ask each contractor for references from projects similar in scope and finish level to yours. Call them. Ask whether the project came in on budget and on time, how the contractor communicated when problems arose, and whether they would hire them again.
Also verify licensing and insurance directly. A certificate of insurance should list you as an additional insured for the duration of the project. This is standard practice, and a contractor who pushes back on it is a contractor to be cautious about. You should also expect to see a line item in their bid for insuring your property during the renovation.
Price Is Not the Same as Value
After all of this, it's worth saying plainly: the right contractor is not always the cheapest one. Renovation is a long, complex, relationship-intensive process. You will spend months in close communication with this person. Their project management skills, their communication style, their subcontractor relationships, and their track record on projects like yours matter as much as the number at the bottom of the page.
The process described here is designed to give you an accurate picture of what each contractor is actually pricing. Once you have that, your decision should account for the full picture, not just the total.
Nubuor Designs is an interior design studio based in Beacon Hill, Boston, working with homeowners across the country on renovations that deserve to be done right. If you're planning a project and want to make sure the process is set up correctly from the beginning, we'd love to hear more about you and your home.
