1. Why an estimate is not a single figure
Three reasons. Some solutions have not been decided at the time the estimate is made.
Some conditions are not known, for instance the ground or the distance to a connection point. They later become a cost or a saving.
The market moves between estimate and quotation, as the construction price index shows: 3.1 % year on year in the second quarter of 2026.
A single figure conceals these three circumstances; a range shows them. That is not caution but precision: a range is a more honest description of what is known.
2. Three things that must accompany it
Without them an estimate is not usable.
| Element | What it shows | How often missing |
|---|---|---|
| Range | how firm the figure is | often |
| Assumptions | which solutions and conditions it rests on | most often |
| Date | an estimate ages | often |
The second is the most important and the most often missing. Assumptions show what would overturn the estimate if it changed. Writing them down also protects whoever produced it, because it shows what they knew and what they did not.
3. What makes an estimate unreliable
Four situations, and none of them requires calculation, only checking. They signal that an estimate is weak.
| Situation | What is left open |
|---|---|
| Completion level undefined | the estimate does not know how far the work goes, and the difference is roughly twofold |
| Ground conditions unknown | the foundation solution is a guess |
| Distance to connection unchecked | one cost is entirely open |
| Price per square metre without an area definition | the denominator of the fraction is uncertain too |
All four are resolvable before the estimate is made. The first needs a conversation with the client, the second a ground survey, the third an enquiry to the network operator, the fourth clarifying one line. None is expensive compared with what their absence does to the accuracy of the estimate.
4. What an estimate is not
Two distinctions prevent misunderstanding. They separate the estimate from the quotation.
| What it is not | The difference |
|---|---|
| A quotation | a quotation binds, an estimate does not |
| A budget | a budget allocates and tracks costs, an estimate states an order of magnitude |
Budgeting and cost control methods are covered in a separate guide. This branch deals with one question: how reliable is the figure we currently have.
5. How to present it
Four elements make a usable document. A range, not a single figure.
A list of assumptions, including completion level, ground conditions and area definition.
A date and the sources used, distinguishing official from commercial. The Statistics Estonia index is official; ranges published by construction companies are not.
A list of what the estimate does not include, referring to excluded costs. The list is presented together with the estimate.
The fourth element prevents the commonest misunderstanding without a single figure having to change. It is the cheapest correction in this entire guide: one list at the end of a document.
In summary, and four practical rules
An estimate as a single figure is incomplete information, because it conceals three circumstances: undecided solutions, unknown conditions and market movement. Three things must accompany it, a range, assumptions and a date, of which assumptions are the most important and the most often missing. Four situations make an estimate unreliable, and all four are resolved by checking rather than calculating.
Four rules: give a range, not a single figure. Write the assumptions out, because they also protect whoever produced the estimate. Distinguish official from commercial sources. Add a list of what the estimate does not include.
This article serves professional orientation at the date of checking. It is not a quotation.