# Servo buying guide: SG90 vs MG90S vs MG996R vs DS3218

> Real torque, stall current and gear material for four common servos, plus the copy versions to avoid and what to pay in India.

Canonical: https://roboticsengineering.in/servo-buying-guide-sg90-mg90s-mg996r/ | Published: 2026-10-27 | Updated: 2026-10-28 | Author: Jignesh Panchal

**Buy the servo that carries the load at the end of your arm, not the one with the biggest number on the listing.** An SG90 is right for a sensor pan and wrong for an arm joint. An MG996R is right for a shoulder and overkill for a gripper that lifts a bottle cap. Torque at the joint and stall current decide the purchase, and both are easy to work out before you pay.

## The four servos side by side

| Servo | Weight | Gears | Quoted torque | Speed | Plan for stall current | Price |
| --- | --- | --- | --- | --- | --- | --- |
| SG90 | 9 g | Plastic | 1.8 kg·cm at 4.8 V | 0.1 s per 60° | up to 0.7 A | ₹120–250 |
| MG90S | 13 g | Metal | 2.2 kg·cm at 4.8 V | about 0.1 s per 60° | about 0.8 A | ₹200–350 |
| MG996R | 55 g | Metal | 9.4 kg·cm at 4.8 V, about 11 at 6 V | 0.17 s per 60° | 2–2.5 A | ₹350–600 |
| DS3218 | 60 g | Metal | about 20 kg·cm at 6.8 V | 0.15 s per 60° | 2.5–3 A | ₹700–1,200 |

*Figures are the values commonly published for each class at the stated voltage. Clones vary, so test the unit you receive. Prices are planning ranges; check current prices.*

Two numbers decide the purchase. Torque tells you what the servo can hold at a given arm length. Stall current tells you what the supply must survive when the joint jams. The second number is the one that resets your Arduino in the middle of a demo.

## What a 9 g servo can actually lift

Torque is quoted at the output horn, so the load falls in proportion to arm length. A 1.8 kg·cm servo holds 1.8 kg at 1 cm and 180 g at 10 cm, and that is the ideal case. Halve it for friction, linkage losses and acceleration, then allow more if the joint takes a shock. The [SG90 guide](https://roboticsengineering.in/components/sg90-servo/) covers the same maths on a single servo.

| Arm length | SG90 (1.8 kg·cm) | MG90S (2.2 kg·cm) | MG996R (9.4 kg·cm) |
| --- | --- | --- | --- |
| 1 cm | 900 g | 1.1 kg | 4.7 kg |
| 2 cm | 450 g | 550 g | 2.3 kg |
| 5 cm | 180 g | 220 g | 940 g |
| 10 cm | 90 g | 110 g | 470 g |

*Load the servo can hold with half the rated torque held back for friction and shock. Static load only; a moving joint needs more margin.*

A gripper that opens 5 cm and holds a 200 g object is at the edge of an SG90. That is why the same gripper feels reliable with an MG90S and strips its plastic gears in a week with the cheaper servo. Move the load from 5 cm to 10 cm on the same jaw and the torque at the horn doubles.

## Why does a cheap servo claim 20 kg·cm?

Because torque figures are easy to print and hard to check. Four things go wrong on cheap listings: the figure is quoted at 6.8 V or 7.4 V while you will run it at 5 V; the servo is a smaller model in a heavier case; the gears are plastic behind a metal-looking shell; or the number is a one-off stall reading rather than a working torque.

Three checks catch most of them before the servo goes into a build. Weigh it: an MG996R is about 55 g and an SG90 about 9 g, so a “standard-size metal-gear” servo that weighs 38 g is not what the listing claims. Turn the horn by hand with the power off: metal gears feel tight and slightly grainy, plastic gears feel smooth and light. Sweep it slowly under a light load and listen: a dry rasp usually means the gear train is not seated properly.

A low price is not proof of a fake. A ₹300 standard-size servo with an honest 6 kg·cm at 6 V can be good value for a gripper. The problem is the listing that promises 20 kg·cm at 5 V for ₹350, because no motor that size delivers it without drawing current you have not planned for. The arrival tests in [where to buy robotics parts](https://roboticsengineering.in/where-to-buy-robotics-parts-india/) apply to servos as much as to boards.

## Voltage, stall current and the supply you need

The three hobby servos are rated for about 4.8–6 V. The DS3218 is quoted at 6.8 V. Running an MG996R straight from a 2S pack at 8.4 V shortens its life, so use a 6 V UBEC or a 6 V supply. The [18650 pack guide](https://roboticsengineering.in/components/18650-battery-pack/) covers the pack side of that wiring.

| Servo | Moving current | Plan the supply for stall | A supply that works |
| --- | --- | --- | --- |
| SG90 | 100–250 mA | up to 0.7 A | 5 V 1 A for two or three servos |
| MG90S | 150–300 mA | about 0.8 A | 5 V 1 A for two servos |
| MG996R | 500 mA–1 A | 2–2.5 A | 6 V 5 A for two or three servos |
| DS3218 | 0.8–1.5 A | 2.5–3 A | 6.8 V 5 A or more for two servos |

*Typical ranges for hobby units. Size the supply for the stall column, not the moving column, and add a capacitor.*

Two rules cover most failures. Do not power a servo from the Arduino 5 V pin or a USB port. Put a 470–1000 µF electrolytic capacitor across the servo supply near the first servo, and connect every ground together. A servo that twitches at rest is usually a supply problem, not a code problem.

## Which servo for which job

| Job | Servo | Why | Watch out for |
| --- | --- | --- | --- |
| Sensor pan or camera tilt | SG90 | Light, fast and cheap; the payload is a few grams. | A binding bracket makes it buzz and overheat. |
| Small gripper | MG90S | Metal gears survive a jam and a dropped object. | Still a micro servo: keep the jaw short. |
| 3-DOF arm shoulder | MG996R | About 9 kg·cm with standard-size mounts and horns. | Needs 6 V, a stiff bracket and a supply sized for stall. |
| Arm that holds a pose under load | DS3218 | Quoted torque near 20 kg·cm at 6.8 V. | Higher current, heavier, and the bracket becomes the weak point. |
| Driving a wheel | Geared DC motor | A converted servo has no torque advantage and poor speed control. | Use a TT motor and a driver instead. |
| Balancing robot | Not a hobby servo | Too slow and too much backlash for a control loop. | A stepper or an encoded DC motor is the correct part. |

*Four of these jobs are servo jobs; two need a different actuator. A servo is a position actuator, not a drive motor.*

## What it costs

| Servo | Servo price | Bracket and hardware | Share of one supply | Realistic cost per joint |
| --- | --- | --- | --- | --- |
| SG90 | ₹120–250 | ₹80–150 | ₹100 | ₹300–500 |
| MG90S | ₹200–350 | ₹100–180 | ₹100 | ₹400–630 |
| MG996R | ₹350–600 | ₹150–300 | ₹150–200 | ₹650–1,100 |
| DS3218 | ₹700–1,200 | ₹200–350 | ₹200–300 | ₹1,100–1,850 |

*Planning ranges, October 2026; check current prices. The supply share assumes one supply running two or three joints. The last column is the number to put in a project budget.*

Price per joint is what a project actually spends. A ₹500 MG996R becomes an ₹850 joint once the bracket and its share of the supply are counted, and a four-joint arm spends nearly as much on power and mounts as on the servos. The [3-DOF arm build](https://roboticsengineering.in/projects/arduino-robot-arm-3dof/) uses three MG996R joints and one SG90, which is the common student split. The [servo torque calculator](https://roboticsengineering.in/servo-torque-calculator/) turns your arm length and load into the torque the joint needs, so you can stop guessing which row applies.

## Common questions

### How many SG90 servos can an Arduino power?

None that move under load. The 5 V pin and the USB port cannot supply the combined stall current. Use a separate 5–6 V supply rated at 1 A per two or three micro servos, and connect the grounds together.

### Can I run an MG996R at 7.4 V?

Not within its rating. It is a 4.8–6 V servo, and a fresh 2S pack sits at 8.4 V. Use a 6 V UBEC. An over-volted servo often works for a while and then fails during the demo, which is the worst possible time.

### Why does my servo buzz when it is not moving?

It is holding against a load or fighting a binding linkage. Centre the horn mechanically, loosen the joint, or move to a servo with more torque. A continuous buzz draws current, heats the motor and shortens the life of the gear train.

If the servo drives a gripper rather than a joint, the [gripper design guide](https://roboticsengineering.in/robot-gripper-design-basics/) shows how servo torque converts into grip force.

Torque and gear material decide whether a walking robot stands up, so read [choosing leg servos](https://roboticsengineering.in/quadruped-robot-guide-india/) before ordering twelve of them.

Servo mounts and horns are usually printed; the [3D printed robot parts guide](https://roboticsengineering.in/3d-printed-robot-parts-design/) covers wall thickness and inserts.

The MG996R can pull over two amps at stall, which is why a shared 5 V rail produces [servo jitter](https://roboticsengineering.in/servo-jitter-problems-fix/) the moment it moves.

Hobby servos stop at a few kilogram-centimetres; the [servo drive selection guide](https://roboticsengineering.in/servo-drive-selection-guide/) covers what comes next.

## Sources and further reading

Documents used to check the numbers on this page:

- [Arduino Servo library](https://docs.arduino.cc/libraries/servo/) — pulse timing and attach() behaviour.
- [Arduino servo motor guide](https://docs.arduino.cc/learn/electronics/servo-motors/) — wiring and power notes.

Last reviewed: October 2026. Specifications are the common published values for these servo classes; clones differ and should be tested on arrival. Prices are Indian retail planning ranges and change with seller and stock.

## Newer builds and guides

- [MG996R servo](https://roboticsengineering.in/components/mg996r-servo/) — Torque, current draw and powering it without brownouts.
- [Servo motor with Arduino](https://roboticsengineering.in/servo-motor-with-arduino/) — Pulse timing, current draw and wiring that stops brownouts.