Vintage Ohmite 1968 Double-Sided Ohm's Law Resistance Calculator Slide Rule USA
DF659
Vintage 1968 Ohmite double-sided electrical calculator combining an Ohm’s Law calculator, parallel-resistance calculator, and standard slide rule in one compact engineering reference tool. This uncommon Made-in-USA promotional calculator is an excellent collectible for electrical engineers, radio enthusiasts, electricians, slide-rule collectors, and fans of vintage scientific instruments.
One side is labeled “Ohmite Ohm’s Law Calculator” and provides scales for calculating relationships among watts, volts, milliamperes, amperes, ohms, and megohms. The reverse is labeled “Ohmite Parallel Resistance Calculator and Standard Slide Rule,” with dedicated resistance scales plus standard A, B, C, and D slide-rule scales.
The sliding center card extends from either side and includes additional printed calculation scales. The Ohm’s Law side is marked “Price $.25,” “Made in U.S.A.,” “© 1968,” and “Ohmite Manufacturing Company, Skokie, Illinois 60076.” The calculator retains its distinctive orange, black, cream, and pale pink graphics, metal-reinforced rivets, and original Ohmite branding.
A desirable piece of vintage electronics history that works equally well as a technical collectible, engineering display item, educational reference, or nostalgic gift.
Sold as is. No warranty from the Seller. No Returns.
SKU: DF659
CONDITION: Pre-owned vintage condition with age-related surface wear, light discoloration, minor spotting, small scuffs, edge wear, and a few faint marks visible throughout. Printed scales and instructions remain generally clear and readable. The center slide is present and moves through the calculator. Metal eyelets show normal aging. No major cracks or large missing sections. Operational accuracy has not been independently verified. See all detailed pictures and read the full detailed description provided by the seller to know what you are purchasing.
Key Features
Type: Specialized electrical slide-rule calculator
Manufacturer: Ohmite Manufacturing Company
Copyright date: 1968
Construction: Laminated or coated fiberboard/plastic-style panels with movable center slide
Double-sided design
Ohm’s Law calculator
Parallel-resistance calculator
Standard A, B, C, and D slide-rule scales
Calculates relationships among watts, volts, amperes, milliamperes, and resistance
Resistance scales include ohms, kilohms, and megohms
Printed operating instructions
Original Ohmite orange-and-black logo
Marked original retail price of 25 cents
Promotional slogan: “be right with OHMITE”
Compact reference tool for engineers, technicians, radio repair workers, and electricians
Made in the United States
Manufacturer and Designer Background
Ohmite Manufacturing Company was established as a manufacturer of resistors, rheostats, and related electrical-control components. The company produced specialized promotional calculators such as this one to help engineers and technicians determine Ohm’s Law values and equivalent resistance without lengthy handwritten calculations.
The Smithsonian identifies an Ohmite Ohm’s Law calculator of this general type as a Perrygraf-produced slide rule. Perrygraf specialized in printed paperboard and plastic calculating devices made for industrial and advertising customers. The calculator’s scales allowed users to determine ohms, volts, amperes, and watts.
The reverse also includes conventional slide-rule scales. Standard slide rules were hand-operated analog calculators widely used by engineers and scientists before inexpensive electronic scientific calculators became common during the 1970s.
Country of Manufacture
United States
The item is plainly marked “Made in U.S.A.” and identifies Ohmite Manufacturing Company in Skokie, Illinois. Comparable Ohmite examples are also categorized as United States-made.
Release Date and Age
Copyright date: 1968
Approximate age in 2026: 58 years old
The printed 1968 copyright date provides a firm date for this particular version. Earlier Ohmite calculators with similar functions were issued in prior decades, but the offered example is the later Skokie, Illinois edition.
One side is labeled “Ohmite Ohm’s Law Calculator” and provides scales for calculating relationships among watts, volts, milliamperes, amperes, ohms, and megohms. The reverse is labeled “Ohmite Parallel Resistance Calculator and Standard Slide Rule,” with dedicated resistance scales plus standard A, B, C, and D slide-rule scales.
The sliding center card extends from either side and includes additional printed calculation scales. The Ohm’s Law side is marked “Price $.25,” “Made in U.S.A.,” “© 1968,” and “Ohmite Manufacturing Company, Skokie, Illinois 60076.” The calculator retains its distinctive orange, black, cream, and pale pink graphics, metal-reinforced rivets, and original Ohmite branding.
A desirable piece of vintage electronics history that works equally well as a technical collectible, engineering display item, educational reference, or nostalgic gift.
Sold as is. No warranty from the Seller. No Returns.
SKU: DF659
CONDITION: Pre-owned vintage condition with age-related surface wear, light discoloration, minor spotting, small scuffs, edge wear, and a few faint marks visible throughout. Printed scales and instructions remain generally clear and readable. The center slide is present and moves through the calculator. Metal eyelets show normal aging. No major cracks or large missing sections. Operational accuracy has not been independently verified. See all detailed pictures and read the full detailed description provided by the seller to know what you are purchasing.
Key Features
Type: Specialized electrical slide-rule calculator
Manufacturer: Ohmite Manufacturing Company
Copyright date: 1968
Construction: Laminated or coated fiberboard/plastic-style panels with movable center slide
Double-sided design
Ohm’s Law calculator
Parallel-resistance calculator
Standard A, B, C, and D slide-rule scales
Calculates relationships among watts, volts, amperes, milliamperes, and resistance
Resistance scales include ohms, kilohms, and megohms
Printed operating instructions
Original Ohmite orange-and-black logo
Marked original retail price of 25 cents
Promotional slogan: “be right with OHMITE”
Compact reference tool for engineers, technicians, radio repair workers, and electricians
Made in the United States
Manufacturer and Designer Background
Ohmite Manufacturing Company was established as a manufacturer of resistors, rheostats, and related electrical-control components. The company produced specialized promotional calculators such as this one to help engineers and technicians determine Ohm’s Law values and equivalent resistance without lengthy handwritten calculations.
The Smithsonian identifies an Ohmite Ohm’s Law calculator of this general type as a Perrygraf-produced slide rule. Perrygraf specialized in printed paperboard and plastic calculating devices made for industrial and advertising customers. The calculator’s scales allowed users to determine ohms, volts, amperes, and watts.
The reverse also includes conventional slide-rule scales. Standard slide rules were hand-operated analog calculators widely used by engineers and scientists before inexpensive electronic scientific calculators became common during the 1970s.
Country of Manufacture
United States
The item is plainly marked “Made in U.S.A.” and identifies Ohmite Manufacturing Company in Skokie, Illinois. Comparable Ohmite examples are also categorized as United States-made.
Release Date and Age
Copyright date: 1968
Approximate age in 2026: 58 years old
The printed 1968 copyright date provides a firm date for this particular version. Earlier Ohmite calculators with similar functions were issued in prior decades, but the offered example is the later Skokie, Illinois edition.