Precision Tool Comparisons · Reviewed October 15, 2026
General Tools 147 vs iGaging 100-333-8B Caliper
Both stainless calipers read decimal inches, millimeters and fractions. General publishes 1/64-inch fractional resolution and auto on/off; iGaging adds IP54 protection and a CR2032 battery.
Best for
Woodworkers, makers and home shops comparing two 6-inch stainless digital calipers with decimal, metric and fractional display modes.
Probably not for
Metrology-lab certification, measurements beyond 6 inches, electrical isolation, hot or moving parts, waterproof use or tolerances tighter than the maker specifications.
Specifications at a glance
| Detail | General Tools 147 | iGaging 100-333-8B |
|---|---|---|
| Range | 0 to 6 in / 153 mm | 0 to 6 in / 150 mm |
| Display modes | Decimal inch, fractional inch, millimeter | Decimal inch, fractional inch, millimeter |
| Resolution | 0.0005 in / 0.01 mm / 1/64 in | 0.0005 in / 0.01 mm / 1/128 in |
| Published accuracy | Plus or minus 0.001 in / 0.02 mm | 0.001 in over 6 in; 2022 catalog lists 0.02 mm |
| Measurements | Inside, outside, depth and step | Inside, outside and depth; frame supports ordinary caliper use |
| Protection | No IP rating published on current page | IP54 moisture and dust resistance |
| Battery | SR44 | CR2032 |
| Included storage | Foam-padded case | Protective case |
| Exact model | 147 | 100-333-8B |
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General Tools Fraction+ Digital Caliper (147)
A 6-inch stainless caliper with an extra-large three-mode display, 1/64-inch fractional resolution, inside, outside, depth and step measurement capability, auto on/off and an SR44 battery.
Pros
- Current maker page clearly states 1/64-inch fractional display resolution
- Auto on/off is documented for battery management
- Step measurement is explicitly listed alongside inside, outside and depth
Cons
- No IP dust or moisture rating is published for model 147
- SR44 battery is different from the iGaging CR2032
- Fractions shown on screen can imply more practical certainty than the accuracy supports
Who it’s for: Choose 147 when 1/64-inch fractions, auto on/off and an explicitly documented step mode fit the workflow. Skip it when an IP54 enclosure rating is required.
Check General Tools Fraction+ Digital Caliper (147) on Amazon Paid linkiGaging IP54 EZ-Cal 6-Inch Digital Caliper (100-333-8B)
A 6-inch stainless digital caliper with an extra-large display, decimal-inch, metric and 1/128-inch fractional resolution, IP54 protection, a CR2032 battery and a protective case.
Pros
- IP54 protection is published for dust and moisture resistance
- Fraction mode resolves to 1/128 inch on the current product page
- CR2032 battery and protective case are documented
Cons
- IP54 does not make the caliper waterproof or suitable for immersion
- Fractional resolution is finer than the published accuracy and should not be confused with it
- Current and older iGaging pages format the model as 100-333-8B and 100-333-8
Who it’s for: Choose 100-333-8B when IP54 protection and 1/128-inch display increments matter. Skip it if an accredited calibration certificate or a range longer than 6 inches is required.
Check iGaging IP54 EZ-Cal 6-Inch Digital Caliper (100-333-8B) on Amazon Paid linkResolution is not the same as accuracy
General Tools lists model 147 resolution as 0.0005 inch, 0.01 mm or 1/64 inch, with accuracy of plus or minus 0.001 inch or 0.02 mm. iGaging lists 0.0005 inch, 0.01 mm or 1/128 inch resolution for 100-333-8B, while its product materials identify accuracy around 0.001 inch over six inches. The display can therefore show increments smaller than the uncertainty stated for the tool.
A 1/128-inch fraction on screen should not be interpreted as proof that a real part is known to that tolerance. Surface condition, jaw pressure, alignment, temperature and technique can shift a reading. Choose a caliper whose documented accuracy is appropriate for the decision, then use its extra display digits for repeatable reading rather than as a substitute for calibration or a more suitable micrometer.
Both cover the common four caliper geometries, with different wording
General explicitly lists inside, outside, depth and step measurements. The outside jaws measure thickness or external diameter; the smaller upper jaws measure internal openings; the rod measures depth; and the shoulder at the end of the beam can compare a step. iGaging documents inside and outside measurement and supplies the conventional depth rod on this stainless frame. Confirm the feature needed from the exact instructions before ordering for a specialized setup.
Good technique changes with the geometry. Keep outside jaws square to the part, avoid cocking inside jaws, hold the beam parallel for depth and seat the step faces fully. Close the jaws gently and use consistent pressure. Do not measure a rotating workpiece, energized conductor or surface hot enough to affect the tool or injure the user. Neither caliper is an electrical safety instrument.
Fraction mode helps woodworking, but the denominator matters
General 147 reduces fractional readings to a 1/64-inch display increment. iGaging publishes 1/128 inch. A finer denominator can be useful when checking nominal lumber, router setups or hardware, but many real woodworking decisions do not benefit from a 1/128-inch screen value. Material movement, cut quality and the tolerance of the next operation may be larger than the difference between the two displays.
Decimal-inch and millimeter modes are usually clearer when tolerances are written numerically. Use the same unit as the plan or mating part rather than repeatedly converting. If a dimension is specified as 12.00 mm, reading a binary fraction adds unnecessary translation. Both calipers switch modes at the display, so the more important choice may be enclosure protection, battery type and control behavior.
IP54 is a boundary, not permission to soak the tool
iGaging labels 100-333-8B IP54 for resistance to dust and moisture. That is a meaningful published distinction because General Tools does not state an IP rating for 147. IP54 does not mean waterproof, immersion-safe or immune to coolant. Keep either instrument away from streams, aggressive fluids and conductive debris, and follow the maker cleaning instructions rather than rinsing the electronics.
Fine dust and chips can also affect the sliding beam and jaw contact even when they do not enter the housing. Wipe the measuring faces with a clean lint-free material before closing the tool. Do not force the slider over contamination. An IP label protects an enclosure under defined conditions; it does not keep a wood chip between the jaws from adding directly to the measurement.
Battery and power behavior affect readiness
General Tools supplies an SR44 battery and documents auto on/off. iGaging uses a larger CR2032 coin cell. Those batteries are not interchangeable, so check what is already stocked in the shop and keep a correct spare in its original packaging. Remove a battery for extended storage when the manufacturer recommends it, and dispose of cells under local rules. Coin and button batteries require especially careful storage away from children.
Before an important measurement session, confirm that the display powers reliably, all segments appear and the mode button changes units correctly. A fading display or intermittent zero is reason to stop and service the tool, not to average questionable readings. Auto-off can preserve power, but it does not establish battery life. This guide makes no runtime comparison because the manufacturers do not publish a shared battery test.
Zero, verify and repeat before trusting a dimension
Clean the closed jaws, bring them together without excess force and zero the display. Reopen and close them to confirm the zero returns. Check a suitable reference of known dimension when the result matters, then measure the part more than once. If rotating the part or tool changes the result beyond the allowed tolerance, inspect for burrs, misalignment, jaw damage or inconsistent pressure.
The included cases protect the sliding and measuring surfaces only when the tool is cleaned and placed correctly. Do not toss either caliper into a drawer with loose abrasives or heavy tools. Avoid using the jaws as scribers, clamps or pry tools. If documented traceability is required, arrange proper calibration and records; a manufacturer accuracy statement and a retail case are not an accredited calibration certificate.
Choose the enclosure and display behavior around the actual tolerance
Choose General Tools 147 when its explicit step-measurement support, 1/64-inch fractions and auto on/off match ordinary shop use. Choose iGaging 100-333-8B when an IP54 enclosure, 1/128-inch fractional display and CR2032 battery are more useful. Both cover a 6-inch class range with stainless frames and three unit modes. Neither is declared more accurate here beyond the manufacturers published figures.
The verified Amazon ASINs are B000UCIGCW for General Tools 147 and B001AQEZ2W for iGaging 100-333-8B. Confirm the exact model and 0-to-6-inch range because both brands sell other sizes and display systems. No price, stock, calibration result, repeatability test, battery-life measurement or personal-use claim is made.
Official sources and further reading
Sources reviewed on October 15, 2026. Prices, availability and terms can change; recheck before buying.
- General Tools: current model 147 range, modes, accuracy, resolution, measurements and battery
- iGaging: current IP54 EZ-Cal display modes, resolution, frame, battery, case and model identity
- iGaging: 100-333-8B range and published accuracy table
- Amazon: exact General Tools 147 listing and ASIN identity
- Amazon: exact iGaging 100-333-8B listing and ASIN identity
Commission disclaimer
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