Converting Between Scales
Converting between grading scales is the attempt to express the same condition judgement in another grading language. It is not normally a matter of dividing, multiplying or replacing one familiar label with another. Different scales can measure different attributes, tolerate different defects, skip different grade intervals and attach different meanings to apparently identical numbers.
Collectors encounter conversion when combining inherited records, comparing auction descriptions, entering certified items into a shared database, preparing sale listings or trying to understand how one service might view another service’s grade. The useful question is therefore not simply “what does this number equal?” It is “which parts of the original condition claim can be carried into the target system, which cannot, and how should that uncertainty be disclosed?”
Governing principle
Convert the meaning of the condition, not merely the number printed on the label.
A sound conversion preserves the original grade, identifies both grading systems, compares published criteria, retains qualifiers and subgrades, uses a range where necessary and distinguishes official equivalency from interpretation.
Core fact
A grade is a claim inside a system
The number, word, letter or symbol on a label has meaning only because a particular grading system defines what was inspected, which defects matter and where its thresholds sit.
Collector rule
Convert meaning before notation
A responsible conversion compares condition criteria, defect tolerances, qualifiers and category rules before it compares the visible number or descriptor.
Recordkeeping rule
Never replace the source grade
The original grade remains historical evidence. A converted grade is a later interpretation and should be stored, displayed and revised separately.
Orientation
Why apparently simple conversions break down
Two grading systems may look compatible while disagreeing about the object, the inspection and the meaning of each step. Exact equivalence fails for several different reasons, and a collector should identify which failure is present before attempting a crosswalk.
The scales may be judging different condition axes
A card scale may emphasise centring, corners, edges, surface and print defects. A comic scale may also weigh spine wear, tears, page quality, missing pages and restoration. A coin scale may distinguish circulation wear, strike, lustre, marks and surface alteration. A packaged toy may divide attention between card or box, blister, figure, seal integrity and completeness.
Where the measured attributes differ, no target number can preserve all the source information. The conversion must either retain those facts separately or admit that it has reduced a multidimensional judgement to a broad tier.
Grade intervals are ordinal, not evenly spaced
A higher grade is better than a lower grade, but the condition difference between adjacent values is not necessarily equal. A tiny extra defect may separate two top grades, while much greater deterioration may sit between two low grades. Percentage arithmetic assumes equal intervals that the grading system may never have claimed.
Scales may skip values or cluster grades
Some systems use only selected numbers in part of the range, then every number near the top. Others use half points, hybrid descriptors or exceptional top grades. The visible range therefore does not reveal how the system distributes its meaningful thresholds.
The same number can occupy a different position
A 9.0 may be one of several high grades in one system, the second-highest whole grade in another, or a label for a substantially different condition band in a third. Identical notation is not proof of identical permitted defects.
Overall grades may be produced differently
One authority may grade holistically; another may average subgrades, weight particular components, apply a weakest-component rule or cap the result when a named defect appears. Converting component scores independently does not reproduce an overall grade unless the authority’s calculation is known.
Collector scenario
The packaged figure marked 85
A collector owns a carded figure graded 85 with component scores of card 85, blister 80 and figure 90. Dividing the overall grade by ten produces 8.5, but that arithmetic says nothing about whether the target scale uses the same component weights, whether an 80 blister caps the overall result or whether the target system treats seal stress and discolouration differently.
If the original authority publishes an official 100-point to 10-point equivalency, the collector can use it as an authorised presentation of the same grade. Without that official bridge, “8.5” should be labelled as numeric normalisation only, while the original 85 and all three subgrades remain the primary evidence.
Evidence hierarchy
Not all conversion methods carry the same authority
Use the strongest available evidence first. Arithmetic belongs at the bottom of the hierarchy because neat numbers cannot compensate for unmatched definitions.
Official same-authority equivalency
The scale owner publishes how two presentations of its own grading system correspond. The underlying inspection standard remains shared, even if the displayed notation changes.
Collector use: Use the published chart exactly, identify its version and retain the original presentation alongside the authorised equivalent.
Definition-based crosswalk
The source and target grade definitions are compared directly: permitted defects, wear, completeness, treatment, surface quality and other category-specific limits.
Collector use: Prefer a target range and state who produced the crosswalk, which categories it covers and whether it is official or interpretive.
Observed crossover evidence
Items graded under one service are later assessed under another, allowing collectors to observe tendencies rather than guaranteed outcomes.
Collector use: Treat results as empirical evidence affected by selection bias, submission strategy, changing standards and unreported failures.
Broad database normalisation
Different grades are assigned to shared internal condition bands so a mixed collection can be filtered or analysed without claiming exact equivalence.
Collector use: Keep the normalised band visibly separate from the source grade and describe it as a cross-category tier, not a professional regrade.
Arithmetic conversion
A number is divided, multiplied or proportionally rescaled to fit another numeric range.
Collector use: Reserve this for sorting, charts or display aids. It does not establish collectible condition equivalence unless the scale owner explicitly authorises the mapping.
Collector workflow
A defensible method for converting a grade
The purpose of the workflow is not to force every source grade into a target box. It is to preserve the evidence, expose the assumptions and stop an approximate interpretation becoming an undocumented fact.
Preserve the source result
Begin by recording the grade exactly as it appears or was originally assigned. Do not tidy the notation, discard the descriptor or overwrite it with the target scale.
- Grading authority or source
- Original grade and named scale
- Descriptor, prefix and suffix
- Qualifiers, designations and subgrades
- Certification number, label generation or date
- Item category and whether the item was graded raw or encapsulated
Identify the exact systems and versions
A company name and a number are not enough. Establish the collectible category, scale version, period of use and any legacy label generation. Standards can change, and a familiar notation may have different meanings across categories operated by the same company.
Determine what each grade measures
Ask whether the grade describes technical condition, overall presentation, a component, completeness, eye appeal, authenticity or a combined judgement. Two scales cannot be aligned responsibly until the collector knows whether they are measuring the same proposition.
Compare condition definitions, not endpoints
Compare the written rules and reference examples. Look for allowed defect number and severity, circulation or handling wear, manufacturing tolerances, structural condition, completeness, restoration, alteration, inspection method and any grade caps.
Carry every material qualifier
The main grade is only one layer of the result. Prefixes, plus grades, stars, page quality, colour or strike designations, restoration status, qualified grades and component scores may contain information the target notation cannot absorb.
Where the target scale has no equivalent field, retain the information as a separate note rather than silently dropping it.
Choose a range where the boundary is uncertain
A single target grade suggests a precision that many crosswalks do not possess. Near a grade boundary, an asymmetric range may be more realistic because the target system could penalise the item’s principal defect more or less heavily than the source system.
Name the method and confidence
State whether the result is an official equivalency, published crosswalk, descriptive mapping, observed-crossover estimate, database-normalised band or arithmetic display conversion. Then record conversion confidence separately from confidence in the original grade.
Regrade when translation cannot answer the question
A conversion interprets an existing grade. It does not physically reassess the item. Where the target system requires evidence that the source assessment never captured, the honest route is a new inspection under the target standard rather than a more elaborate conversion table.
Interpretation
Ranges, boundaries and confidence
Conversion is least reliable at precisely the points collectors most want certainty: where a small shift changes a grade, a registry position or a substantial amount of market value.
Use ranges to expose uncertainty
“Approximately 8.0-8.5 under the target definitions” is often more defensible than “equals 8.5.” A range acknowledges that the source and target boundaries do not align perfectly.
The range may be asymmetric. A source 8.5 might map mainly to target 8.0-8.5, while occasionally reaching 9.0 if the target system is more tolerant of the item’s decisive defect.
Separate two kinds of confidence
Grade confidence asks how securely the source grade describes the item. A verified certified grade may have high source confidence.
Conversion confidence asks how securely that source grade maps into the target system. The same item can have high grade confidence but low cross-scale confidence.
Domain boundary
Conversion is not regrading, crossover or valuation
Conversion
Interprets an existing grade in another notation without independently examining the item.
Regrading or crossover
A target grader assesses the item under its own standards. A table cannot guarantee the outcome, and crack-out submission adds physical and evidential risk.
Valuation
Market value also reflects trust, liquidity, holder, population, guarantees and buyer preference. A mapped condition grade does not create equivalent price data.
Scale-specific judgement
Where collectors need extra caution
Descriptive words are not universal categories
Mint, Near Mint, Excellent, Very Fine, Fine, Very Good, Good, Fair and Poor appear across collecting fields, but their order and defect expectations vary. “Fine” may be a formal circulated band in one field, a mid-range technical grade in another and merely complimentary prose in an antiques listing.
Tie every descriptor to a named scale. Preserve hybrid terms such as VF/NM or NM/M because they indicate a position between defined bands and contain more information than a simplified word or number.
The 1-70 coin scale is not a percentage system
Coin grades separate categorical states such as circulated and Mint State, and they do not use every number evenly throughout the range. An MS-60 coin has no circulation wear but may still show numerous marks, hairlines or a weak strike. AU-58 and MS-60 are separated principally by the presence or absence of wear, not by a simple two-point quantity.
Dividing 58 by 70 and calling the result an 8.3 cross-category grade discards the coin-specific meaning of friction, lustre and high-point wear. At most, it is a mathematical index.
Shared 10-point company scales remain company-specific
Card grading services may all use a visible 10-point range while differing in half-point availability, centring tolerances, surface weighting, factory-defect treatment, subgrades, qualifiers and the distinction between Gem Mint and Pristine. Top-tier grades occupy comparable market positions, but they do not automatically permit identical defects or cross at the same nominal number.
Legacy grades require historical interpretation
Older catalogues, dealers and national traditions may use obsolete proprietary numbers or familiar words under unfamiliar standards. Preserve the original wording, publication and year. Determine its period meaning before mapping it to a modern range. “Mint” in a historic sales list should not be silently upgraded into a modern certified top grade.
Warning signs
Common conversion mistakes
These errors usually make a record look cleaner while making the underlying claim less trustworthy.
False linearity
Mistaken claim
An 85 on a 100-point scale must be 8.5 on a 10-point scale.
Better judgement
That is valid only where the authority publishes the equivalency. Otherwise it is numeric normalisation, not a grade conversion.
Identical-number fallacy
Mistaken claim
Both systems say 9.0, so the items have the same condition.
Better judgement
The systems may tolerate different defects, inspect different attributes or place 9.0 at different conceptual positions.
Cross-domain overreach
Mistaken claim
A comic graded 8.0 is equivalent to a card, coin or toy graded 8.
Better judgement
Different domains judge different evidence. Use a broad condition tier if cross-category comparison is genuinely needed.
Qualifier loss
Mistaken claim
A restored 8.0 can be recorded simply as an 8.0 in the target scale.
Better judgement
Treatment, alteration, incompleteness and qualified status must remain explicit because they materially change the grading claim.
Private-to-public inflation
Mistaken claim
My inventory note says 9/10, so I can advertise the item as a professional 9.
Better judgement
A private score does not become a certified grade through conversion. Preserve its source and describe it as collector-assessed or seller-assessed.
Price-guide substitution
Mistaken claim
Once I map the grade, I can use the target company’s price guide.
Better judgement
Grade conversion is not value conversion. Brand reputation, holder, registry demand, guarantees, liquidity and market trust can all affect price.
Documentation
How to record a conversion without erasing its history
A structured registry should preserve the source evidence as immutable history while allowing later conversions to be revised when standards, research or crosswalks improve.
| Field | Purpose |
|---|---|
| Original grade | Exact notation shown or assigned |
| Scale and authority | Named system, company, dealer or collector source |
| Category and version | Collectible type, standard generation or historic period |
| Descriptor and affixes | Words, prefixes, suffixes, plus or star designations |
| Qualifiers and subgrades | Restoration, alteration, completeness and component evidence |
| Certification and date | Verification reference and grading chronology |
| Converted result | Target grade, range or normalised band |
| Method | Official, descriptive, empirical, normalised or mathematical |
| Conversion confidence | Strength of the mapping, independent of source-grade confidence |
| Source and notes | Crosswalk reference, exclusions, assumptions and later revisions |
Strong record
Official same-authority presentation
- Original grade: AFA 85
- Scale: standard 100-point presentation
- Unified presentation: 8.5 under the authority’s published equivalency
- Subgrades: card 85 / blister 80 / figure 90
- Method: official equivalency
- Confidence: high
Cautious record
Unofficial descriptive mapping
- Original grade: seller-assessed Near Mint
- Normalised tier: high grade
- Approximate range: 8.5-9.4
- Method: descriptive comparison only
- Confidence: low
- Warning: not professionally graded and not equivalent to a certified 9-grade item
Public wording
Language that reveals rather than conceals
Prefer
- Approximately corresponds to...
- Broadly comparable with...
- Normalised to the internal high-grade band...
- Mapped using the published grade descriptions...
- Officially presented by the grading authority as...
- Estimated range rather than an exact crossover...
Avoid
- Exactly the same as...
- Guaranteed to cross at...
- Equivalent value...
- Automatically becomes...
- Universally accepted conversion...
- Professional grade language for a seller-assigned score...
Cross-category collections
Normalise to condition tiers, not fictional universal grades
A multi-category collection may need common filters, but a universal numeric grade usually implies more equivalence than the evidence supports. Broad tiers can serve the database while category-specific facts remain primary.
Exceptional
Essentially flawless under the relevant category standard.
Mint
No meaningful use, with only negligible flaws permitted by that domain.
High grade
Minor defects with strong overall presentation.
Above average
Noticeable but limited defects and better-than-typical survival.
Average
Ordinary wear or several moderate defects.
Below average
Heavy wear, a major defect or substantially reduced presentation.
Poor
Severe damage, major incompleteness or structural failure.
Specialist threshold: when not to convert
Stop at the original record and seek category expertise or a fresh assessment when the source scale cannot be identified, the label generation is uncertain, the object may have changed since grading, essential qualifiers are missing, the target system depends on uninspected features or the conversion will influence a high-value sale, insurance schedule or legal dispute.
The absence of an honest conversion is itself useful information. It tells the next collector that the historical grade has been preserved but should not be treated as a current target-system judgement.
Key takeaways
- Numbers and descriptors are labels for category-specific standards, not universal measurements.
- Official same-authority mappings are the strongest conversions; arithmetic is usually only a display aid.
- Original grades, qualifiers, designations and subgrades must remain visible.
- Ranges are often more truthful than exact target grades, especially near valuable boundaries.
- Grade confidence and conversion confidence answer different questions and should be recorded separately.
- Conversion is not regrading, does not predict crossover and does not establish equivalent market value.
- Cross-category collections should use broad condition tiers while preserving domain-specific evidence.
- A conversion should disclose its source, method, version, assumptions and limits.
Continue learning
Qualifiers and Modifiers
Review the extra words, symbols and designations that must travel with a grade when it is translated.
Back to Scales
Return to the Scales sub-domain and its full topic sequence.
Limits of Scale Precision
Continue to why fine-looking grade intervals do not necessarily represent equally fine or reliable distinctions.
Related topics
Numerical Scales
Understand why grading numbers are ordinal labels for standards rather than universal measurements of percentage condition.
Descriptive Scales
Examine why familiar words such as Fine, Excellent and Near Mint change meaning between collecting fields.
Domain-Specific Systems
See how coins, cards, comics, toys and other objects require different condition axes and grading priorities.
Grading Boundaries and Thresholds
Explore why conversion becomes least reliable where small defects decide whether an item crosses a valuable grade boundary.