Precise and approximate quantification
1. The number and its framing: count or estimate
Readers of scientific writing interpret every number together with a signal indicating how much they can trust it as precise. This signal comes from the words before the number (exactly, approximately), the form of the number itself (1,306 or 1,300), and the way the data were collected. The rule is not about individual words but about aligning three things: what is known about the data, how many digits you write, and which framing you choose.
Exactly emphasizes that the stated value should be understood precisely in the given context. Approximately indicates an approximation: it may be an estimate of an unknown quantity or a rounded presentation of a known result. A measured value has uncertainty, even when it is written with many digits.
The number 1,306 is often understood as a detailed count, but the notation itself does not prove the origin or accuracy of the data. Exactly and precisely add emphasis. A total of merely summarizes: a total of approximately 1,300 is also possible.
exactly + number: emphasis on precision · approximately + number: approximation · a total of + quantity: total
The trial enrolled exactly 120 patients.
The trial enrolled exactly 120 patients.
Exactly asserts the precise number of participants; this can be checked against the study data. The sentence itself does not describe the counting method.
Roughly 40 patients withdrew before the second visit.
Roughly 40 patients withdrew before the second visit.
The exact number is not important to the argument, so the framing is approximate and the number is round.
A total of 1,306 households returned the questionnaire.
A total of 1,306 households returned the questionnaire.
A total of summarizes the quantity; the detailed number is presented here as the result of a count.
2. Precise markers and when they are appropriate
Exactly and precisely directly emphasize precision. A total of, in all, and in total indicate a sum, while n = 214 indicates the sample size; these forms are not interchangeable markers of precision. A total may be either precise or approximate.
Exactly and precisely are also appropriate in statements about ratios that genuinely hold: exactly half of 64 plots is 32. If the ratio only approaches one half, a different framing is needed.
For mass, time, or concentration, distinguish the specified value, the instrument reading, and measurement uncertainty. Precisely 12.5 millilitres may emphasize dosing to the stated value, but one decimal place alone does not prove that degree of precision. A scientific report needs appropriate information about the method and uncertainty.
exactly / precisely + number: a precise value in context · a total of / in all: total quantity
Exactly half of the 64 plots were irrigated.
Exactly half of the 64 plots were irrigated.
32 out of 64 really is half, so exactly is justified.
Precisely 12.5 millilitres of the solution was added to each flask.
Precisely 12.5 millilitres of the solution was added to each flask.
Precisely emphasizes the specified dosage; the reliability and uncertainty of the measurement must be described separately.
The archive holds 8,214 letters in all.
The archive holds 8,214 letters in all.
In all comes after the number and summarizes the count.
3. Approximate markers and their register
Neutral and formal approximate markers include approximately, roughly, around, about, some (only before a number: some 200 delegates), in the region of, of the order of, and close to. Among these, approximately and in the region of sound the most formal, about and around are neutral, roughly is slightly more informal, and of the order of emphasizes the order of magnitude itself.
Or so comes after a quantitative expression: forty minutes or so. In forty-odd days, the suffix -odd means “forty-something,” that is, somewhat more than forty, not any deviation in either direction. These forms are less formal. For approximate dates, use c. or ca. (circa): c. 1450. The symbols ~ and ≈ are also possible in scientific writing when they are part of the accepted notation.
Some in the form some 200 is an approximate estimate, whereas in some delegates without a number it indicates an indefinite quantity: these are two different phenomena, and only the first is being practiced here. Also, “an estimated 300,000” already contains approximation: estimated functions as an estimation marker.
approximately / roughly / around / about / some + number · number + or so · number-odd · c. + year
Approximately 30 per cent of the lectures were recorded.
Approximately 30 per cent of the lectures were recorded.
A formal approximate marker before a round percentage.
Some 200 delegates attended the opening session.
Some 200 delegates attended the opening session.
Some before a number means “approximately” here.
The manuscript dates from c. 1450.
The manuscript dates from c. 1450.
C. is a standard abbreviated marker for approximate dates.
Interviews lasted forty minutes or so.
Interviews lasted forty minutes or so.
Or so comes after the number and makes it approximate.
The fund is in the region of £4 million.
The fund is in the region of £4 million.
In the region of is a formal fixed expression that requires these exact function words.
4. Do not mix frames in one expression
In an ordinary statement about one value, exactly roughly 300 or precisely about 300 creates ambiguity: it is unclear what exactly is being called precise. Approximately around 40 duplicates the approximation. For concise academic writing, one marker is usually enough; this is an editorial principle, not a ban on all nested estimates.
A known count can be given precisely or rounded for an overview: 412 students in a table and about 400 in an introduction are compatible. Approximately 412 is not a grammatical error: such a number may be an estimate, for example from a model. But if the required figure here is the exact count 412, the approximate marker is unnecessary.
Different frames can coexist in one sentence if they refer to different numbers: the exact number of plots and the approximate proportion among them. Each number then has its own frame, so there is no contradiction.
specify what was counted, what was estimated, and what was rounded; do not duplicate markers unnecessarily
Approximately 62% of the samples failed the stress test.
Approximately 62% of the samples failed the stress test.
One approximate frame is used with one number.
A total of 412 students completed the course.
A total of 412 students completed the course.
The quantity was counted, so the total formula is used without approximately.
Exactly 64 plots were sampled, and roughly a third showed erosion.
Exactly 64 plots were sampled, and roughly a third showed erosion.
The exact quantity and the approximate proportion do not conflict because they refer to different numbers.
5. The number of digits must match the precision of the data
The number of digits determines the detail of the notation, but it does not prove the precision of the measurement. 114.8 mm is written to the nearest tenth of a millimetre; the actual uncertainty may be different. Give as many digits as are justified by the method, the uncertainty of the result, and the purpose of the report.
For a sample of 30 people, 14 responses are 46.666…%, which can be rounded to 46.67% or 47%, depending on the required level of detail. Decimal places do not add confidence about the whole population. In a concise presentation, 14 of 30 often shows both the count and the denominator most transparently.
Roughly 46.83% is not intrinsically impossible: approximate estimates can also include decimals. However, excessive detail can mislead the reader. For a general overview, roughly 47% is often more appropriate; for a technical result, explain the uncertainty and the rounding used.
the detail of the number must match the data and the purpose; uncertainty is not determined by the number of digits alone
Of 30 respondents, 14 supported the plan.
Of 30 respondents, 14 supported the plan.
The count and denominator make the result transparent; a percentage can also be given if needed.
The balance reads to the nearest gram, so the mass is given as 86 g, not 85.62 g.
The balance reads to the nearest gram, so the mass is given as 86 g, not 85.62 g.
The number of digits is tied to the instrument’s resolution.
Roughly 47% of the plots were flooded.
Roughly 47% of the plots were flooded.
A rounded number naturally combines with an approximate marker.
6. Directional approximations: nearly, almost
Nearly and almost are not neutral: they indicate that the value falls slightly short of the stated number. Nearly 50 volunteers means, for example, 47 or 48 people, not 52. Neutral approximately, roughly, and around do not indicate a direction and are suitable when deviation in either direction is equally likely.
Therefore, choose nearly and almost when the data really are slightly below a round value and you want to show an approach to it; when the direction of deviation is unknown, use a neutral word. Boundary expressions meaning “at least,” “no more than,” or “over” belong to a different rule concerning qualified quantification, while comparisons (“one third more,” “the highest”) belong to the rule on comparative and superlative forms.
For proportions, useful expressions include roughly a third, around one in five, and almost two thirds. A fraction is not necessarily approximate: one of three equal parts is exactly a third. An approximate marker is needed when the ratio itself is only approximate.
nearly / almost + number = slightly below; approximately / roughly / around + number = near it, without direction
Nearly 50 volunteers took part.
Nearly 50 volunteers took part.
This expresses an approximation from below: probably 47–49.
Approximately 50 volunteers took part.
Approximately 50 volunteers took part.
A neutral estimate: it could be 48 or it could be 52.
Almost two thirds of the loans were repaid early.
Almost two thirds of the loans were repaid early.
A fraction with directional approximation: the proportion is just below two thirds.
7. From table to text: reporting verbs and formulas
Totalled, numbered, amounted to, and stood at report a quantity or level, while was estimated at and an estimated explicitly identify an estimate. The first group does not guarantee precision: enrolment totalled approximately 3,400 students is possible.
When moving from a table to prose, you can round a known number and signal this. From roughly three-quarters, you cannot recover the specific 73.4% without additional data. In every section, provide the level of detail required by its argument.
The exact count exactly 3,420 in a table and about 3,400 in an introduction are compatible: the latter is a rounded description of the former. Check that they refer to the same data and that the rounding is appropriate. Do not attribute to a rounded number a precision it does not have.
totalled / stood at: quantity or level · was estimated at / an estimated: explicit estimate
Enrolment totalled 3,420 students.
Enrolment totalled 3,420 students.
Totalled reports a total; this example gives the detailed number without an approximation marker.
Visitor numbers were estimated at 300,000.
Visitor numbers were estimated at 300,000.
Was estimated at marks an estimate of the number of visitors. The estimate itself may have a specific numerical value without guaranteeing the exact real number.
An estimated 300,000 visitors came to the festival.
An estimated 300,000 visitors came to the festival.
An estimated comes before the number as an approximate marker.
Common mistakes
Incorrect:Exact 62% of the samples failed the stress test.
Correct:Exactly 62% of the samples failed the stress test.
For an exact numerical quantity, the adverb exactly is required, not the adjective exact.
Incorrect:A total 412 students completed the course.
Correct:A total of 412 students completed the course.
The pattern a total of + quantity requires the preposition of.
Incorrect:Rough 47% of the plots were flooded.
Correct:Roughly 47% of the plots were flooded.
Before a number used as an approximate estimate, the adverb roughly is required, not the adjective rough.
Incorrect:Approximately 40 interview were coded.
Correct:Approximately 40 interviews were coded.
After 40, the countable noun must be plural: interviews. Approximately indicates an approximate quantity and does not cancel the plural.
Incorrect:The number was estimate at 3,000 visitors.
Correct:The number was estimated at 3,000 visitors.
In the passive, the past participle estimated is required after was. At introduces the numerical value of the estimate.