Mastering the Past Tense of ‘Cost’: Usage, Rules & Examples

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The verb “cost” is one of the most frequently used verbs in English, especially when talking about money, prices, or expenses. However, its past tense form often confuses learners—even advanced speakers and writers. Is the past tense “cost” or “costed”? When do you use each one? These questions arise because “cost” behaves differently depending on the context, leading to common mistakes.

Mastering the correct past tense of “cost” is essential for clear and accurate communication in everyday conversations, shopping, business negotiations, financial discussions, exams, and writing. Whether you’re buying groceries, analyzing a project budget, or describing a costly mistake, using the right past tense form ensures your message is understood and grammatically correct.

This comprehensive guide will provide an in-depth, step-by-step explanation of how to use the past tense of “cost,” including plenty of examples, tables for quick reference, and practice exercises. It’s perfect for students, teachers, ESL learners, business professionals, and grammar enthusiasts seeking absolute clarity and mastery over this tricky verb.

Table of Contents

3. Definition Section

3.1. What Does ‘Cost’ Mean?

As a verb, “cost” primarily means “to require payment of a specified amount”. It refers to the price or amount you must pay for something.

As a noun, “cost” means the amount of money required to purchase something or the expense involved. However, in this article, we focus on its use as a verb.

Examples in present tense:

  • The laptop costs $1,000.
  • This service costs too much.
  • The repairs cost less than we expected.
  • How much does the ticket cost?
  • It costs a lot to maintain a car.
  • Moving abroad costs time and money.
  • The treatment costs thousands of dollars.

3.2. Grammatical Classification of ‘Cost’

“Cost” is an irregular verb in its main meaning related to price. Unlike many verbs, its base form, past simple, and past participle are identical: cost – cost – cost.

It is also a transitive verb, meaning it requires a direct object (what the payment is for).

3.3. Function of ‘Cost’ in Sentences

Primarily, “cost” acts as a main verb that expresses the price of something:

  • “The shoes cost $50.”

It can also mean “to cause the loss of something valuable”:

  • “His mistake cost him his job.”
  • “Speaking out cost her her reputation.”

3.4. Contexts of Usage

  • Everyday shopping: “How much did this dinner cost?”
  • Business and economics: “The company’s expansion cost millions.”
  • Figurative expressions: “It cost me a lot of time.”

Below is a quick reference for the forms of “cost” in its price and calculation senses:

Verb Form Base Past Simple Past Participle
Main meaning (price) cost cost cost
Pricing calculation cost costed costed

Table 1: Present, past, and past participle forms of “cost”

4. Structural Breakdown

4.1. Irregular Verb Patterns

For its main meaning (price or expense), “cost” is an irregular verb. The past simple and past participle forms remain the same as the base form: cost – cost – cost.

This is similar to other irregular verbs with no change:

  • put – put – put
  • set – set – set
  • hit – hit – hit
  • cut – cut – cut

4.2. Regular Verb Alternative: ‘Costed’

When referring to the action of estimating or calculating costs, especially in professional or technical contexts, the verb “cost” becomes a regular verb. Its past simple and past participle forms are “costed.”

This usage is less common and specific to cost estimation.

4.3. Summary of Forms

Verb Form Base Past Simple Past Participle Example Sentence
Main meaning (price) cost cost cost The book cost $10.
Pricing calculation cost costed costed The engineer costed the project.

Table 2: Forms and example sentences for ‘cost’ and ‘costed’

4.4. Sentence Structures with Past Tense of ‘Cost’

  • Subject + cost + amount/time/effort
  • The tickets cost $200.
  • The mistake cost him his job.
  • It cost us a lot of time.

Passive Voice:

  • The repairs were costed by the contractor.
  • The mistake cost him dearly.

4.5. Pronunciation Notes

  • British English: /kɒst/ or /kɔːst/
  • American English: /kɑːst/
  • “Costed” is pronounced /ˈkɒstɪd/ or /ˈkɑːstɪd/ — note the added syllable -ed.

5. Types or Categories

5.1. Category 1: ‘Cost’ with Monetary Meaning (Irregular Past = Cost)

Use “cost” when referring to the actual price paid or amount spent at some time in the past.

Examples:

  • The shoes cost $50 yesterday.
  • That phone cost me a month’s salary.
  • Lunch cost less than expected.
  • The concert tickets cost $200 each.
  • The repairs cost $500 last month.
  • How much did the jacket cost?
  • It didn’t cost very much.

5.2. Category 2: ‘Costed’ in Financial Calculations or Estimations (Regular Past)

Use “costed” when referring to the action of calculating, estimating, or pricing out a project, plan, or item.

Examples:

  • The accountant costed the new proposal last week.
  • The engineer costed the bridge project carefully.
  • The project was fully costed before approval.
  • The finance team costed the renovations last month.
  • They costed the event at $10,000.
  • All options were thoroughly costed before choosing one.

5.3. Category 3: Idiomatic and Figurative Usage

Use “cost” (irregular form) when referring to figurative loss, sacrifice, or consequences.

Examples:

  • His decision cost him his reputation.
  • The error cost the company millions in damages.
  • Her honesty cost her some friends.
  • The war cost many lives.
  • His arrogance cost him dearly.
  • Poor planning cost us valuable time.
  • Their carelessness cost them the championship.

5.4. Summary Table 3: Categories Overview

Category Correct Past Form Example Usage
Monetary Transaction cost The dress cost $100.
Calculating/Evaluating Cost costed The accountant costed the new proposal.
Figurative (loss, sacrifice) cost The error cost him his job.

This table helps clarify which form to use in different contexts.

6. Examples Section

6.1. Simple Past Statements

  • The meal cost $20.
  • The repairs cost me a fortune.
  • The software upgrade cost the company thousands.
  • The dress cost $70 on sale.
  • The holiday cost less than we planned.
  • The taxi ride cost $30.
  • His mistake cost him a promotion.

6.2. Negative Sentences

  • The tickets didn’t cost much.
  • The mistake didn’t cost us anything.
  • The repairs didn’t cost as much as I feared.
  • The new phone didn’t cost more than $600.
  • Her honesty didn’t cost her any friends.

6.3. Questions in Past Tense

  • How much did the book cost?
  • Did the vacation cost a lot?
  • Did your mistake cost the company money?
  • How much did those shoes cost?
  • Did it cost more than expected?

6.4. Passive Constructions

  • The project was costed by the finance team.
  • The new system was costed at $1 million.
  • The renovations were costed carefully before approval.
  • The design was costed by the engineers.
  • The proposal was costed before submission.

6.5. Complex Sentences and Idiomatic Use

  • His arrogance cost him his friends and his career.
  • The accident cost the company millions in compensation.
  • The scandal cost her her reputation and her job.
  • The delay cost us valuable time and resources.
  • Ignoring the warning signs cost them dearly.
  • The risky investment cost him his savings.
  • The war cost thousands of lives and billions of dollars.

6.6. Comparison Table 4: ‘Cost’ vs. ‘Costed’ Examples

Context Correct Past Form Correct Example Incorrect Example
Price paid (transaction) cost The laptop cost $800. The laptop costed $800.
Estimation/Calculation costed The designer costed the blueprint. The designer cost the blueprint.
Loss consequence cost His actions cost him his friends. His actions costed him his friends.

6.7. Mini-dialogues with Past Tense of ‘Cost’

  • A: How much did your new phone cost?
    B: It cost $700, but it was worth it.
  • A: Did the repairs cost a lot?
    B: No, they didn’t cost much at all.
  • A: Who costed the project?
    B: The finance team costed it last month.
  • A: Did your mistake cost the company money?
    B: Unfortunately, yes. It cost us thousands.
  • A: Was the proposal costed before submission?
    B: Yes, it was carefully costed by the accountants.

6.8. Summary Table 5: 15 Quick Examples by Context

Context Example
Monetary The ticket cost $50.
Monetary The dinner cost less than $30.
Monetary Question Did the book cost much?
Monetary Negative It didn’t cost anything.
Estimation (Calculation) The architect costed the new design.
Estimation Passive The project was costed by experts.
Estimation They costed the event at $5,000.
Figurative Loss His error cost him the contract.
Figurative The scandal cost her her career.
Figurative The decision cost us valuable time.
Monetary The shoes cost $80 last week.
Estimation The builder costed the renovation carefully.
Monetary The holiday cost a fortune.
Figurative Poor planning cost them millions.
Estimation The new policy was costed before implementation.

7. Usage Rules

7.1. Rule 1: Use ‘cost’ (irregular) for the amount paid in the past

  • The concert cost $100.
  • The car cost less than $10,000.
  • Her new dress cost only $30.

7.2. Rule 2: Use ‘costed’ (regular) when meaning ‘to calculate or estimate cost’

  • The engineer costed the bridge project.
  • The accountant costed the new plan last week.
  • They costed the event in detail.

7.3. Rule 3: Negative and Interrogative Forms

Use did + base form (cost) in negatives and questions, regardless of meaning:

  • Did the car cost much?
  • It didn’t cost a lot.
  • Did they cost the renovation carefully?
  • They didn’t cost the project correctly.

7.4. Rule 4: Passive Voice Usage

  • The building was costed by experts.
  • The proposal was costed at $2 million.

7.5. Rule 5: Idiomatic and Figurative Expressions

  • His mistake cost him dearly.
  • The war cost thousands of lives.
  • Poor planning cost us valuable time.

7.6. Rule 6: Avoiding Overuse of ‘Costed’

“Costed” is rare and mainly used in professional, technical, or accounting contexts when discussing estimation or calculation. For most everyday uses, use “cost.”

7.7. Exceptions and Special Cases

  • Do not use “costed” to refer to the actual price paid.
  • Do not use “costed” in idiomatic expressions about loss or sacrifice.
  • Always use “cost” in negatives or questions, since the auxiliary “did” requires the base form.

7.8. Summary Table 6: Usage Rules with Examples

Rule Example
Transaction (irregular) The bag cost $30.
Calculation (regular) The proposal was costed last month.
Figurative loss (irregular) The scandal cost him his reputation.
Negative It didn’t cost a lot.
Question Did the tickets cost much?
Passive (estimation) The building was costed by professionals.
Incorrect to say “The shoes costed $50.” (wrong)
Correct to say The shoes cost $50.

8. Common Mistakes

8.1. Mistake 1: Using ‘costed’ for past transactions

  • Incorrect: The shoes costed $50.
  • Correct: The shoes cost $50.

8.2. Mistake 2: Using ‘cost’ for cost estimation actions

  • Incorrect: The accountant cost the new plan.
  • Correct: The accountant costed the new plan.

8.3. Mistake 3: Incorrect past tense questions

  • Incorrect: How much did it costed?
  • Correct: How much did it cost?

8.4. Mistake 4: Misusing in negative sentences

  • Incorrect: It didn’t costed much.
  • Correct: It didn’t cost much.

8.5. Mistake 5: Confusing ‘cost’ as noun vs. verb

  • Incorrect: The cost was costed high. (confusing noun and verb)
  • Correct: The cost was high. (noun phrase)
  • Correct: The project was costed at $2 million. (verb in passive)

8.6. Table 7: Common Mistakes with Corrections

Incorrect Correct Explanation
The trip costed a lot. The trip cost a lot. For transactions, use irregular ‘cost’.
The engineer cost the project. The engineer costed the project. For estimation, use regular ‘costed’.
It didn’t costed much. It didn’t cost much. After did, use base form ‘cost’.
How much did it costed? How much did it cost? After did, use base form ‘cost’.
The laptop costed $1,000. The laptop cost $1,000. Transaction price = irregular ‘cost’.
The proposal was cost by experts. The proposal was costed by experts. Passive of estimation = ‘costed’.

9. Practice Exercises

9.1. Exercise 1: Fill-in-the-Blank

  1. The repairs _____ $500 last month.
  2. The accountant _____ the new plan carefully.
  3. His mistake _____ him his job.
  4. The holiday didn’t _____ very much.
  5. The project was _____ by experts.
  6. The shoes _____ $80 on sale.
  7. They _____ the renovations at $20,000.
  8. The laptop _____ $1,200.
  9. Who _____ the event expenses?
  10. The delay _____ us valuable time.

9.2. Exercise 2: Correct the Mistake

  1. The tickets costed too much.
  2. The engineer cost the design.
  3. It didn’t costed anything.
  4. The proposal was cost by the team.
  5. How much did the phone costed?
  6. The scandal costed him his reputation.
  7. The accountant cost the project yesterday.
  8. Her honesty costed her some friends.
  9. They didn’t costed the new plan yet.
  10. The laptop costed $900 last year.

9.3. Exercise 3: Identify the Context

Choose whether “cost” or “costed” fits better.

  1. The firm _____ the project last week. (estimation)
  2. The new shoes _____ $100. (price paid)
  3. The decision _____ him his promotion. (figurative loss)
  4. The proposal was _____ before submission. (calculation)
  5. The dinner _____ less than $30. (transaction)

9.4. Exercise 4: Create Sentences

  1. Write a sentence about a past purchase using “cost”.
  2. Write a sentence about an estimation using “costed”.
  3. Write a sentence about a mistake with figurative “cost”.
  4. Write a question in past tense using “cost”.
  5. Write a negative sentence in past tense using “cost”.

9.5. Exercise 5: Sentence Transformation

Change from present to past tense.

  1. The shoes cost $60.
  2. He costs the new building project.
  3. Her mistake costs her her job.
  4. They cost the renovation carefully.
  5. The tickets don’t cost much.

9.6. Answer Key

Exercise 1 Answers:

  1. cost
  2. costed
  3. cost
  4. cost
  5. costed
  6. cost
  7. costed
  8. cost
  9. costed
  10. cost

Exercise 2 Answers:

  1. The tickets cost too much.
  2. The engineer costed the design.
  3. It didn’t cost anything.
  4. The proposal was costed by the team.
  5. How much did the phone cost?
  6. The scandal cost him his reputation.
  7. The accountant costed the project yesterday.
  8. Her honesty cost her some friends.
  9. They didn’t cost the new plan yet.
  10. The laptop cost $900 last year.

Exercise 3 Answers:

  1. costed
  2. cost
  3. cost
  4. costed
  5. cost

Exercise 4 Sample Answers:

  1. The TV cost $500 last month.
  2. The accountant costed the project carefully.
  3. His mistake cost him his reputation.
  4. How much did the concert tickets cost?
  5. The repairs didn’t cost much.

Exercise 5 Answers:

  1. The shoes cost $60.
  2. He costed the new building project.
  3. Her mistake cost her her job.
  4. They costed the renovation carefully.
  5. The tickets didn’t cost much.

10. Advanced Topics

10.1. Historical Development of ‘Cost’ and ‘Costed’

“Cost” comes from Old French coste (expense), from Latin constare meaning “to stand firm” or “to be fixed.” As a verb, it’s been irregular historically. The regular form “costed” emerged later for clarity in technical contexts.

10.2. Regional Variations

In British English, “costed” is more commonly used in professional budgeting or accounting. In American English, “costed” is less frequent but understood in technical contexts. For price paid, both varieties use “cost.”

10.3. ‘Cost’ as Past Participle in Perfect Tenses

  • It has cost us a lot so far.
  • It had cost them dearly before the mistake was fixed.
  • By then, the repairs had cost thousands.

10.4. Subjunctive and Conditional Forms

  • If it had cost less, we would have bought it.
  • Had it costed more, the board might have rejected it. (rare, technical)

10.5. Using ‘Costed’ as Adjective or Participle

  • A fully costed proposal
  • A carefully costed project
  • Well-costed estimates

10.6. Nuances in Figurative Language

  • It cost him his peace of mind.
  • The scandal cost her her friends and trust.
  • The accident cost many their lives.

10.7. Summary Table 8: Advanced Usage Scenarios

Scenario Example
Perfect tense (monetary) The repairs have cost over $2,000.
Perfect tense (figurative) His arrogance has cost him dearly.
Conditional If it had cost more, we might not have bought it.
Passive participle (estimation) A fully costed proposal was submitted.
Regional/technical The project was costed last quarter. (UK/technical)
Subjunctive Had it cost less, everyone would be happy.
Figurative idiom Poor decisions cost him his happiness.
Perfect passive The event has been costed at $5,000.
Historical The war had cost millions of lives.
Continuous The repairs are costing us more every day.

11. FAQ Section

  1. Is the past tense of ‘cost’ always ‘cost’?
    Usually, yes. When talking about the price paid or a figurative loss, the correct past tense is irregular: cost.
  2. When should I use ‘costed’ instead of ‘cost’?
    Use costed only when referring to the calculation or estimation of costs, often in professional, technical, or financial contexts.
  3. Why do some people say ‘costed’? Is it wrong?
    In most cases, yes, but “costed” is acceptable when describing the process of pricing, not the payment. It’s wrong when referring to the transaction price paid.
  4. Is ‘costed’ accepted in American English?
    It’s less common but accepted in professional, financial, or technical contexts related to cost estimation.
  5. Can ‘costed’ be used in everyday conversation?
    Rarely. It sounds technical. In everyday speech, use “cost” for price or loss.
  6. How do I form negative past tense sentences with ‘cost’?
    Use didn’t + cost: “It didn’t cost much.”
  7. What is the past participle of ‘cost’?
    For price or loss, it’s cost. For estimation, it’s costed.
  8. Can ‘cost’ be used figuratively in the past tense?
    Yes. E.g., “His carelessness cost him his job.”
  9. Does ‘cost’ change in continuous or perfect tenses?
    No. Use cost as the past participle: “It has cost us dearly.”
  10. Is ‘costed’ only used in financial or technical contexts?
    Yes. “Costed” mainly refers to cost estimation or calculation.
  11. Are there regional differences between ‘cost’ and ‘costed’?
    Yes. UK English uses “costed” more often in professional settings. US English prefers “cost” except in technical contexts.
  12. How can I remember when to use ‘cost’ vs. ‘costed’?
    If talking about money paid or loss: use cost.
    If talking about calculations or estimates: use costed.

12. Conclusion

The verb “cost” is irregular in its main sense, so the past tense is usually “cost”, not “costed.” This applies when talking about the price paid, emotional or figurative loss, and most everyday situations.

“Costed” is correct only when referring to the calculation or estimation of costs, which is more common in technical, accounting, or professional contexts.

Remember to carefully consider the context: is it about the amount spent, or the process of pricing? Review the many examples, tables, and exercises above to reinforce your understanding.

Mastering this subtle distinction will enhance your accuracy and professionalism in both written and spoken English.

Keep practicing, revisit the FAQs and advanced topics as needed, and soon the past tense of “cost” will come naturally to you!

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