Watts to HP Formula Calculator and Conversion Chart for Canadian Homes and Workshops

The watts-to-HP conversion is simpler than most people expect. Mechanical horsepower = watts ÷ 745.7. For example: 1,000W = 1.34 hp, 2,000W = 2.68 hp, and 5,000W = 6.71 hp. Multiply that horsepower by 745.7, and you have the watts back. That constant is not a guess. NIST defines 1 mechanical horsepower as 745.6998715 W, and it is the same figure used on North American equipment nameplates.

Here is where it gets interesting, though. That formula converts units only. A motor rated at 1 hp can pull far more than 746 W from your supply. We will show you exactly why.

Takeaways

• Mechanical horsepower utilizes 745.7 W as its constant. This NIST-verified figure is the standard on most Canadian and North American equipment nameplates.

• A 1 hp motor is not a 746 W load. Efficiency, power factor, and starting current push actual draw well above that, often reaching 1,200 W or more at running speed.

• Startup surge can reach 4 to 8 times the running current. Oklahoma State University Extension confirms this for induction motors, which matters when sizing any backup power source.

• Metric horsepower (PS) uses a different constant. 1 PS equals 735.5 W, not 745.7 W, a gap that matters on engine specs and imported equipment.

• Backup power sizing needs more than an HP number. Continuous output, surge capacity, and total simultaneous load all need to line up before a power station can safely run a motor.

Converting Between Watts & Horsepower

Most Canadians working with tools, pumps, or motors deal with mechanical horsepower. That is the North American standard, and the focus here.

Turning Watts into Mechanical Horsepower

There is one formula to implement here. This is:

Horsepower = Watts / 745.7

Figure out a 2,237 W case here. This gives close to 3 hp. NIST defines 1 mechanical horsepower as 745.6998715 W. That's approximately 745.7 W. 746 W is used mostly as shorthand. That is rounding only, not a different standard.

Going from Horsepower Back to Watts

Do the calculation in reverse as follows:

Watts = Horsepower x 745.7

Consider a 2 hp motor case. This equals 1,491.4 W at the shaft. A 5 hp motor works out to 3,728.5 W. These figures describe mechanical shaft output only, not actual electrical input from your supply.

Mechanical Horsepower Compared to Metric Horsepower

Canada uses both standards. Mechanical HP covers most North American equipment. Metric horsepower, or PS, appears on some European engine and vehicle specs.

The 2 constants are not interchangeable:

• 1 mechanical hp = 745.7 W

• 1 metric hp / PS = 735.5 W

The difference is approximately 10 W/unit. The difference is not noticeable on a small motor. For high-output engines, the gap can be thousands of watts. That can impact generator sizing. Thus, check the label. This helps to see what standard your equipment is.

Conversion Chart for A Quick Reference

This table tracks watts in the 100-5,000 scale. It utilizes two NIST constants. The first case is the mechanical HP (745.7 W). The second one is 735.5 W, or metric PS.

Use the mechanical HP column for North American pumps and workshop tools. The PS column applies only when the spec sheet explicitly states metric horsepower.

Running the Watts to HP Calculation Step by Step

The math works on any phone watts-to-HP calculator. Here are 2 cases: one in each direction.

Working Out the Horsepower from 1500 Watts

Our case here is a table saw. This features a 1,500 W motor. Thus;

1,500 / 745.7 = 2.01 hp

That is just over 2 mechanical hp. In metric PS, divide by 735.5 for 2.04 PS.

Calculating Watts from 1 Horsepower

Reverse it with a 1 hp pump:

1 x 745.7 = 745.7 W

That is the shaft output only. It's not what the pump draws from an outlet. The real demand is higher, and the next section shows why.

Why a 1 HP Motor Pulls More Power Than You Might Expect

That 1 hp motor can surprise you. It can easily draw 1,000-1,600 W. The figure may even exceed that. Two factors explain the gap.

How Efficiency and Power Factor Drive Up Electrical Input

A motor nameplate describes shaft output, not electrical input. Motor efficiency and power factor are separate factors that affect electrical input. Efficiency describes how much electrical power becomes mechanical output, while power factor describes the relationship between real power and apparent power in an AC circuit. You cannot calculate actual electrical watts from efficiency alone. A motor rated at 1 HP provides 746 watts of mechanical output, but the electrical input will be higher because of efficiency losses and reactive current. A typical 1 HP motor may draw around 1,000 to 1,400 watts when fully running, depending on its design, efficiency, and power factor.

Understanding Locked Rotor Amps at Startup

The Canadian Electrical Code (CE Code) Part I treats unmarked locked rotor current as 6 times the full-load current rating from the nameplate. Oklahoma State University Extension confirms the broader range of 4 to 8 times full-load amps for several seconds. You will find this listed on the nameplate as Locked Rotor Amps (LRA). It also varies by motor design. Thus, your nameplate is the only reliable source for that figure.

What a Rural Pump Motor Nameplate Actually Shows

There is one thing common to rural Canadian properties. That's the 1 hp, 230V single-phase submersible well pump. A representative motor in this class shows:

• Rated shaft output: 1 hp

• Continuous running input: approximately 1,200 W at rated current

• Maximum running input: approximately 1,600 W

• Startup demand: Locked Rotor Amps can exceed 40 A, which at 230V produces approximately 9,200 VA apparent startup demand for the first few seconds.

That gap between shaft output and startup demand is what the hp-to-watts formula cannot show you. You will want to verify the LRA from the manufacturer's submittal sheet before sizing any power source for a motor.

Putting These Numbers to Work When You Need Backup Power

Knowing the real draw behind a horsepower rating helps when choosing backup power. When sizing a generator or power station, convert HP to watts first, then check running watts and locked rotor amps. Running a motor from a portable power station or a home battery backup system means checking 3 things: continuous output, surge capacity, and total simultaneous load.

Matching Continuous Output and Surge Capacity to Your Motor

Start with the motor's running wattage from the nameplate, then check the LRA for the startup spike. A power station needs to cover both:

• Its continuous output should cover running watts with some headroom.

• It is essential that its surge capacity is able to withstand the LRA surge without tripping.

With a 1,024 Wh LiFePO4 battery, the BLUETTI Elite 100 V2 provides 1,800 W continuous power and 3,600 W surge power. The BLUETTI Elite 100 V2 can support smaller single-phase loads within its rated output limits, though starting capability depends on the motor's actual LRA.

Big tools need something like the BLUETTI Apex 300. Its strong 2,764.8 Wh battery feeds you 3,840 steady watts. With Power Lifting, BLUETTI Apex 300 can temporarily support up to 7,680W for compatible loads that require higher startup power. Compatible 120V and 240V equipment can be supported depending on the system configuration and electrical requirements. For 240V pumps, compatibility depends on the pump's actual electrical requirements, including running watts and locked rotor amps. You can even tie batteries together to get 100 kWh.

Accounting for Everything Running at Once

Motors almost never run by themselves. Add up the running watts of everything you plan to use at once. Make sure your power station can handle that total number. The last motor you turn on will add a huge power spike on top of that. Planning for this total load keeps your power from tripping.

The Watts to HP Conversion Is a Starting Point, Not the Whole Answer

The 1 hp to watts formula is reliable and NIST-verified. Divide watts by 745.7, and you get mechanical horsepower. That is solid for comparing equipment on paper.

What it cannot do is tell you how much energy a motor actually consumes. Efficiency, power factor, and locked rotor amps all affect the real electrical demand, which can be well above 745.7 W per hp. In our experience, working from the nameplate rather than the HP label is what keeps you from undersizing a backup system. Use the chart to get oriented. Also, consider the nameplate to get an accurate reading.

FAQs

How many watts to get a horsepower?

By the exact rules, it is 745.7 watts. For quick math, almost everyone uses 746 watts.

1,000 watts means how many horsepower?

You find that by dividing 1,000 by 745.7. You find nearly 1.34 mechanical hp. In metric PS, divide by 735.5 instead for about 1.36 PS.

Is motor horsepower the same as the power it draws?

Not at all. The HP rating is just the work pushing out. It takes way more power going in to make that happen. Expect a 1 HP tool to pull close to 1,000-1,400 watts.

How much juice kicks over a 1 HP motor?

It is totally different for each one. They may require 4–8 times their running current during startup.

Can a portable power station run a 1 hp motor?

It depends on the motor's running watts and LRA, not the hp label alone. The BLUETTI Elite 100 V2 offers 1,800 W continuous and 3,600 W surge, which covers some motors in this class at running speed, but checking the motor's actual LRA against those numbers is what confirms it will start.